Why would oil be forcing out of eng after head rebuild?

Thank you for reply. 2 cylinders dropped valve seats. Machine shop says they've seen this before. The pistons had just superficial scratches and no damage to cylinders. In fact cylinders were smooth with no lip indicating good wear. My mechanic showed me this before we took head to machine shop. Pistons appear tight as well. Most of damage was to head. Car is back at mech so I will suggest compression and leak down tests. Also will make sure vacuum/pvc system ok.

Ok, but if there was ANY damage to the pistons ring lands, (the edges) well just saying. Now i am not doubting the mechanic, just making suggestions!! I sure can't argue with someone that can SEE the engine. Dont mean any disrespect at all.

This gets stranger still. Mech saying oil is not only being forced out the dipstick, but also out the pcv. Claims I need to do full short block now for an additional $1700. Compression seems ok as motor runs great. The mach shop that did the head told mech they could not find a core for the head and had to weld on metal to my head then cut back down to stock specs. Any chance a oil padsage or vent hole was covered up in this process?

Compression SEEMS ok ? This engine , in MY opinion, should have been replaced to start with! I think the ring groves that the piston rings ride in are compressed (damaged) which binds the rings letting compression rush by. But then i can't see it so my thoughts are moot. If you ever do figure this out, i'd like to kmow, thanks.