the exception to the rule about not sanding too fine is wet sanding
with oil. then you can go as fine as you want. sanding to 600 grit
with watco leaves a gorgeous surface

I would do this on the lacquer top coat for to get nice consistent
scratches on the sruface to increase sheen, but not on the wood surface
itself. If you spray anything on a surface sanded this fine, the finish
will simply bead off. It will not adhere.

Unlikely. Many finishes incorporate wetting agents or are otherwise
formulated to deal with surface tension issues. I've sprayed shellac,
lacquer, varnish, oil-based poly and water-based urethanes on surfaces
sanded to 600 grit without any application problems or long-term adhesion
problems.