There is a problem in handling basses, they don't fit the body. Two main brenches of holding the instrument developed, the open and closed position, holding the instrument in a different angle to the body. Then there are the players using french grip and the ones using german grip with differnt angles between hand and strings. The mentioned variables and the differnt body types and sight ability of the players sum up to very few players holding the double bass identically. The same can be watched in different degrees with other instruments. I think, the differences increase with the size of the instrument.
If you check the flute players, there bodies or chairs are usually turned to different angles and the flutes and heads are dropping more or less to the side.
As long as the sound is OK, don't worry to much for the look. Large sections of stringed instruments are distributed over quite a lot of space and will always have the F holes pointing in several directions when seen from the listeners. Each player has to see the conductor and is turned to him, not to the people listening. In many halls, the spectators are very well distributed, too, maybe even behind or above the players. The only person sure of the best sound turns out to be the conductor.