This is a requirement if Framework wants to supply Windows licenses at an OEM discount. And let’s face it - there are more Windows Framework users than Linux Framework users. Without this discount, it puts them at a considerable competitive disadvantage.
This covers all the prebuilt devices, the DIY version doesn’t count as a prebuilt which is why you pay the retail price of Windows. But to add one without the Windows key means they have to add one version for every language. And that adds a lot of complexity
…but what if they sell the blank key cap individually, as a purchase option? The keyboard can stay as is. Hell, even key caps (all of them or individually) as replaceable parts. e.g. WASDERT (depends on language and layout), space bar and Enter keys get worn out sooner than others in general.
That is, find ways to do it, instead of having answers for not to do it.
FYI you could get the blank ANSI or ISO layout and place on the symbols you want on the keys. granted you don’t get that zero z height smoothness and the perfect precision of machine placement of the text.