confirmed, actually it appears to be just for OPFOR...
repo - start a new map, place your unit and place the sites module for OPFOR BASE option, the rest of the options, leave default. then preview... What I did is this, placed several of them along the airfield and around the airbase. When you get in the game (preview or mp), you will notice that only 2 units will spawn for each site placed. This was not an issue 3 or 4 dev builds ago and needs to be looked into.
Tested even further... place a few OPFOR module sites set on BASE, and on the other side or near, placed a few sites for BLUFOR set to base as well... what you will find is going to be that all the OPFOR sites spawn 2 units and all the BLUFOR sites spawn all normal units (around 19-20) with vehicles...
This issue only affects OPFOR sites with base setting... this may also affect the other settings for OPFOR as well, but I never used them to have an idea of the unit spawn count when used, I do know that OPFOR sites base is broken.