There is no provision in the Windows license agreement that directly refers to the change of hardware, its improvement and modification. MAR and TPR agreements are different stories, where changes to the motherboard and processor are reserved:

6. Refurbish, Remanufacture, Repair.
The TPR must have a documented process and implementation to refurbish a qualifying device that includes at least the following steps:
          (a)Testing
                     (i)Random Access Memory (RAM) and/or Fixed Storage Disk are replaceable.
                                   (ii) processor cannot be swapped. They can only be replaced if they are defective, they must be replaced with components of the same specification as the original.
         (b)Cleaning.
Re-used hard drives should be formatted according to the media erasure guidelines published in the National Institute of Standards and Technology Special Publication 800-88 or similar.

But the topic is not so simple and obvious because you should start with what Microsoft understands by the new device. Well, if the system (in the OEM version it is assigned to the device), each significant change to the hardware requires the purchase of a new license; after such a change, the computer is treated as a new device.
The technical effect of this solution is the need to reactivate after making a significant hardware change.
And so in the case of expanding the RAM, changing the hard disk, adding expansion cards, these changes are considered irrelevant because they do not directly affect (maybe with the exception of changing the HDD to SSD) the performance and capabilities of the device.
However, if you change your processor or motherboard, replacing them is considered a major hardware modification.

The 4K Hardware Hash mechanism introduced in Windows 10 is a technical implementation of these reservations. This mechanism generates a 4096-byte unique hardware identifier, which is a representation of a given device. Many system elements are used for the calculation, e.g. model and serial number of the motherboard, MAC addresses of network cards, model and serial number of the processor, etc. The very mechanism of creating 4K HH is secret and is created using the OA3Tool.exe tool. Individual components have different … let’s call it “weights”, the specification of the motherboard has the highest importance here. But back to the licensing agreement…

There is a certain mess when it comes to the technical aspects of the functioning of the software and the provisions of the license agreement. Microsoft departed from the directly expressed objections to the way the software was used, replacing it with a certain enigmatic entry and opening a door to potentially illegal activity. Specifically, point 2c (iv):

(…) For example, this Agreement does not give the Licensee any right to: (…) avoid the technical restrictions and limitations of the software;

This directly means that if the software detects a significant change in hardware and informs you about the need to use a new license, you must follow the instructions, otherwise it will be considered a violation of the license agreement. 6:

(…) During activation (or reactivation required by changing the components of a given device), the software may detect that the installed instance of it is a non-genuine or improperly licensed product or has been altered in an unauthorized manner. After a failed activation, the software will attempt to repair itself by replacing the non-genuine Microsoft software with genuine Microsoft software. The licensee may also receive reminders about the need to obtain a legal license for the software. Successful activation does not confirm that the software is genuine or properly licensed. Actions to circumvent or bypass activation are not allowed. For more information to help you determine if your software is genuine or properly licensed, please visit (aka. ms/genuine). Some updates, support and other services may only be offered to users of genuine Microsoft software.

This means that the 4K HH based software decides whether a given hardware change was acceptable or not (in which case a new license is required) and then informs the user of this fact.
We will not find here records regarding specific components, as was the case with, for example, Windows 7.

In turn, on the page: https://support.microsoft.com/pl-pl/help/20530/windows-10-reactivating-after-hardware-change
is clearly described what should be done before changing the hardware in order to restart activation was successful, circumventing the software’s technical protections.
In my opinion, the scale of the phenomenon was so small (modifications and improvements) that the manufacturer abandoned the use of direct reservations in the license agreement, however, leaving technical measures to hinder significant changes.
Then, it made it possible to practically freely change the equipment by providing instructions on how to do it.
In the case of a software legality audit, a significantly modified device may raise doubts and, depending on the scale of changes, may be considered as equipment for which there is no software license.