We should always be setting az and especially el/alt for any data we take. One reason is that the cosmic ray distribution depends on the orientation of the detectors.
In the case of test stands and SLAC this information may not be available, and it's not worth putting a lot of effort into getting it. However, for anything delivered to Rubin on the mountain (including Level 3) we should be setting valid values.
It'd be nice to get them from LSSTCam in the Cerro Pachón cleanroom, but that may also be too hard to be worth the trouble.