I kind of suspect that it's a way of sorta walking back the "sure, put 5 in a 1BR that sleeps 4!" rule, because it seems to be misunderstood and often even a nuisance. Lots of DVC members show up and are surprised there's no bed and are surprised the resort won't give them a cot.
The last resort they did with a "sleep 5 in a 1BR BYOB" was in 2004, Saratoga. Everything since has slept 5 native - AKV (2007), BLT (2009), VGC (2009), Aulani (2011), VGF (2013). Poly doesn't count, no 1BRs.
CCV did 4 in a studio, 4 in a 1BR. The 1BR is one of the smallest in the system at 680 square feet. I think this was a deliberate walk back.