In an animation a shaft is rotating. The end of the shaft sticks out of a housing. Is there any rationale for modeling the hole in the housing when the shaft will stick out even if there is no hole?
It all depends on the level of realism you are trying to achieve. Little touches like that can add a lot to an image, but if that part isn’t going to be very visible, it won’t matter.
You don’t have to model the whole hole, either. You can just extrude an appropriate shape inward a bit around the axel, and then either set the interior faces black, or use shadow casting light, and/or keep your angel low enough to the hole so you can’t see that it just ends.
I just did about the same thing today, actually. Well, it’s a gun mounting on an organic-ish spaceship, but it’s still a rod going into a solid body. Here’s some shots if it helps. I highlighted the interior faces for clarity. I could probably just delete the back four and that inner vertex if it dosn’t mess with the shape of the subsurface too much, because there’s no gaps for someone to see through to the inside faces or whatever.