Part would be sample, but also because, like everything on this team, Wemby.
With Wemby on the court, the opposition shoots a higher %age of attempts (253 out of 615 attempts are 3s, which translates to a 3PAr of 41.1%, or around 14th in the league compared to 6th in the league we have now) at 37.5% (still would have only ranked 26th in the league out of 30 teams). They shoot worse because we have players who can guard them tighter, but attempt more because it's tougher to drive into the paint (or they had to kick it out to the perimeter for open threes when we inevitably collapse to over help).
With Wemby off the court, the opposition shoots a lower %age attempt (87 out of 255, which translates to a 3PAr of 34.1%, or best in the league) at 46% (by far the worst in the league). Teams get to choose their offence like an all you can eat buffet, they can drive inside for an open layup, OR they can kick it out on wide open three point shooters.
Given we have the 7th slowest pace in the league, it suppresses our 3PA and as such we have the lowest 3PA with the highest 3% against. At least that's my hypothesis.