I have that seatpost. Angling the saddle downward does move the clamp forward, but you can still move the saddle aft-ward as far as the rails allow.
The offset of the clamp does depend on saddle angle. I don't know if the advertised 32mm offset is when the saddle is angled up all the way, angled down all the way, or in the middle.
There's an older version of the Gran Cru seatpost in which the offset doesn't change with saddle angle, if you can find one.
The IRD WayBack has the most offset available, I think.
https://www.interlocracing.com/shop/...t-wayback-2418
edit: looks like there were some issues with that old style Grand Cru seatpost:
https://velo-orange.blogspot.com/201...per-clamp.html