Originally Posted by KULTULZ
... Tapping a cam gear onto a cam while installed may move the rear cup outwards and cause unwanted cam play. ...
Actually, the cup has no influence on cam end play in the SBF, and all thrust clearance is established between the cam gear, thrust plate, and cam. I know you're thinking of another engine family.
I agree that any thumping on the cam can knock the cup further out, leading to leaks or failure.