: Vinyl estimator wants to install vinyl under the tub in our completely refurbished bathroom. Is this a good idea or should we install the tub before the vinyl goes down?

If the floor is level, this can be good. Check the floor with a level first.
If the floor is not level, there will be a gap between tub and floor when the tub is shimmed up to level. On no-level floors, the 1/2" subfloor goes a long way to cover these things up. Terry