Look closely at the picture from the previous thread (NOT this occurance).
The hollow cast-in-place post on the inside of the broken bit of the cover (the post that locates the spring) is squashed and deformed looking to me. All c0cked and catawampus too.
Enough force involved in that to do the deed to the cover, certainly.
Remember there is a substantial perforated sheet metal column dead center of the filter's axis that would transfer significant force back to the cover if there was something assembled incorrectly.
How it happened is up to conjecture -- yeah, I'd be looking at that filter to be the filter that fits another bike, not this one. Or else I'd be looking at mash marks on the wrong side of the filter for the dreaded backwards assembly oops thing.
I like this picture, I hide a larger-than-the-filter-diameter supermagnet inside the same exact space that was involved in this breakout issue. So I know there is room in there normally.
Oldfeller