The Celtics list Hauser at 6'-7". At the draft combine, he measured as follows:
Measured 6'-6.75? barefoot, 6'-8.0? in shoes 8'6.0? standing reach, 217.4 lbs, and 6'-9.25? wingspan at the 2021 NBA Draft Combine
He is not even 6'-7" barefoot. Barefoot is how the league tracks height now and that is how they measure me when I go to the Doctor. Some players can be not even 6'-7" and play as a big/PF, but Hauser is not one of them. He does not rebound well enough. Averaged only 3.5 Rebs/game last season (a career high), and that is on a team that hardly plays bigs.
Gordon Hayward is also listed at 6'-7" but 225 lbs, so he is bigger/beefier than Hauser. Gordon Hayward averaged 4.4 rebs/gm for his career with seasons as high as 6.7 rebs/gm. Even Gordon Hayward is a better rebounder than Hauser. Hayward is a 2/3, just like Hauser is a 2/3.
These days, there isn't all that much difference between a 2/SG and a 3/SF, they are both essentially wings, almost interchangeable. But there is a bigger difference between a wing/SF and a big/PF. You can be a 3/4, a SF/PF swing or whatever you want to call it but it requires a greater level of versatility than being a 2/3. Hauser does not have that level of versatility.
Hauser mostly played in line ups where there were 2 guards (most often Pritchard and Holiday) along with Tatum and a big. He also played 3rd most with White, Brown, Horford, and Porzingis. This latter one, you could have Hauser as a guard or a forward. I know the majority see this differently but I like Hauser as a guard. His height is an advantage if he plays as a SG, easier to shoot over people. I like him fine as a SF too. But I do not like him at all as a PF.