6.1 Cam swap questions

Instructions for cam removal include -

Remove accessories,
remove front cover
remove cam sprocket and chain
remove rocker gear and pushrods
rotate camshaft twice and the lifters will be "retained" in their bores.
remove camshaft

Questions:

1 - Interested in exactly how the roller lifters are "captured" when the cam is rotated prior to removal.

2 - Also, after install.....what actually happens to release them back onto the lobes?

Are they pushed back down out of the bores by the pushrods or?

3 - Lastly - do I need to "degree" the replacement cam from the Aftermarket?...............or is the grind quality good enough not to worry about it?