Solid cam questions.

Well if you are talking about LA, R or RB they don't oil through the pushrod anyway. The oil comes through the head into the rocker saft to oil the top end.

With engines that oil through the push rod there is still a hole in the lifter that allows oil to pass through it up the push rod to oil the top end.

A solid lifter just doesn't have a piston in it that takes up all the clearance in the top end. Because of that you have to set valve lash with some clearance to allow for expansion as the engine heats up.