I can't tell you for sure, but it feels off if the deal was changed compared to what it was stated as before. But you probably should have pushed a bit harder on them formalizing the STAK agreement earlier. Still, it could be nothing at all and maybe they simply aren't aware that your original deal was a different one, but such things rarely (if ever) happen by accident.

Also: there are ways to use a STAK to screw the stak certificate holders out of their rightful share during a liquidity event so make sure that you know who represents the STAK, ideally a notary public should be assigned as the administrator of the STAK, and not someone in the management. Best of luck!