OK, let's look at this in more detail ....
Homes games
LAC, IND, WAS, OKC, TOR . . . .
Those are 50/50 matchups, let's say, but since they're at home it's 55%
MEM, CHI, ATL, BRK, CHA . . . .
Those are bad teams, and the Celts are at home, so let's give them 80%.
Let's say 6/10 there. Seems reasonable to me. 7/10 also seems doable.
Now, road games.
HOU, TOR ... those are rough games, I'll give the Celts 33% to win.
CHI, NYK, PHX, SAC, ORL ... those are bad tanking teams, I'll give the Celts 67% to win.
DET, MIN, NOR, POR, UTA, MIL, WAS ... Let's say here the C's have a 40% chance on the road.
All told, let's go with 7/14 on the road.
In total, if I'm looking at this from a granular perspective, it seems totally reasonable to think they might go 13-11 or 14-10.
I really don't see it for the people who think they're gonna go <.500 the rest of the way.