McCullough was injured before he really got going. He played pretty well for a guy's first 16 games. I know I was devastated when he was injured, as I really thought he was going to be good. Through his first half a season, he averaged 9.6 points 6.9 rebounds and 2.1 blocks, certainly a decent start. I would be mildly disappointed if Freeman puts up that kind of line, but certainly not ready to call him a bust.
On your other point, a TS of .531 isn't great until you consider Brisset only had a career .481 TS. Guys like Mintz (.524) Filipowski (.534) and RJ Barrett (.532) were major freshman contributors on about that kind of TS%.
Freeman's efficiency will depend a lot on his usage... If he's disciplined enough to only shoot when he's open, only drive and post up when he's got a clear advantage over his defender, his usage will be low, but his efficiency will be very high. I think we'd prefer the middle of the road if his aggressiveness creates enough success, even if his TS% is a little low. A lot depends on how good everybody else on the team is doing.