Not odd when you consider the turret ring of the T-62 extends a considerable distance over the tracks. While the same holds true for the M48/M60 and M1s, it isn't to the same extent as the T-62. What does that mean? It means one can't simply look at the turret ring diameter as the determining factor for crew space within the confines of the turret. The T-62, regardless of the turret ring diameter, has far less usable space for the crew than contemporary western tanks.
the roof is much lower than on NATO tanks. Seat and storage arrangements also can waste precious space. Also the cannon breech is quite large which also takes up space. The ejector mechanism also wants some space.
Ironically the 115 mm fixed cartridge ammuniiton is one of the longest used in tanks today.