Since currently there is only one level, this will obvciously only run once on that level for the time being.
This is mainly used for CCMDs and CVARs which either print some diagnostics or change some user-settable configuration.
This will now both exclude floor caps when only ceiling elements are used and everything outside the bounding box of active portal lines.
Hopefully this is enough to fix the issues with portal caps but of course it is not foolproof if someone just makes the right setup.
Apparently they can indeed happen with broken map setups like isolated linedefs somewhere in the wild (see Strife MAP08.)
Although they are a problem for triangulation, this isn't what sections get used for currently so it's of no real concern.
In case this is needed later their work data gets marked as 'bad' for the time being.
