This is true!
I have a slightly older VLTOR and a brand new ACS. Here's some photos with my comparative observations: (hope this helps)
Side by side: the ACS is exactly an inch longer than the VLTOR with the buttpad.
http://imageshack.us/a/img26/7730/img0371ut.jpg
ACS cheek real estate:
http://imageshack.us/a/img607/8789/img0370gc.jpg
VLTOR cheek real estate:
http://imageshack.us/a/img692/7521/img0369wc.jpg
Side by side from above. You can clearly see the length difference, but the width and cheek real estate seem to be almost identical. Both are very comfortable when mounted and both establish a good cheek weld, but I have only shot the VLTOR (and I loved it).
http://imageshack.us/a/img15/9273/img0367jm.jpg

