Is there an instruction on what not to put in a multipolygon relation?

I use OSM-Inspector:multipolygon to check my inputs and correct accordingly.

While doing so I also correct other contributions if I think I can improve/correct them. Sometimes I find some very complex geometrical structures that, in my opinion, show that either I or some other contributors do not fully understand the multipolygon construct.

I have read and reread the help pages on this issue but nowhere could I find a list of objects that should not be considered as holes within a multipolygon. I have found buildings=, leisure=, sport=, etc. defined as "inner". I thought these objects are to be excluded from the multipolygon relation. NOTE: For example OSM-Inspector does not find buildings defined as "inner" to be an error!

So are the instructions clearly written, i.e. I missed them! My mistake: Sorry: Bad question!

Or should the instructions include a list of objects that are not to be part of an multipolygon area!