I guess if the valve was only bent slightly, the pressure of the valve spring,,,,,May flex the head on to the seat. just kind a thinking out loud here.
I don't know that answer to that: I often wondered if that would happen. But the OP could pull the valves, put a light spring in, and THEN test with liquid.
I know for me, I would have them checked at a shop and I do all sorts of things myself if I can; this one is beyond my tooling. At a shop, they would spin them in their valve machine, and know right away. (But those are really precise and super steady, and I would not expect something like a drill press to be precise and steady enough.)