I recently launched at attack with a dozen or so BMP-3's with just their default 2 man crews on board (I'd forgotten the above issue existed), as fire support for a couple of mounted BTR mech platoons.   Within a few turns I realized something was seriously wrong , when I had negligible spotting contacts from them, except from the vehicles with the BMP platoon HQ's on board. Essentially, I had a company's worth of BMP-3's that were useless, and gave up the battle as a waste of time.