Is truing the action necessary?

[Robinhood]

I figured that once you have the scope dialed in, nothing moving out of place on the barreled action, stock, scope or scope mounts, and you have the reticle plumbed to your bubble level, as long as you keep that sucker level, you were good to go whether the front of the action was trued or not.

This is an assumption based on the belief that the scope and the barrel are in a parallel axis. If you have a barrel action junction that skews the barrel, then your assumption is incorrect.