Well, most Amstrad boards I have found did have a quasi-mechanical switch...a linear spring inside the key cap that presses a contact between two membranes. Same principle as the Model M, without buckling and tactility.
I was lucky last time i bought from this seller. I bought 5 vintage boards for $11 that I had no idea about and manged to get a blue alps board and 2 fujitsu leaf spring keyboards.