If references points to [COLOR=rgb(39,42,52)]reference_loot_template ONLY than the SQL example above can’t be declared as an example of a self-reference.
Inserting 21215 in field reference in creature_loot_template than would (as I understand you) point to [COLOR=rgb(39,42,52)]reference_loot_template. Where is the self-reference ?
Selfreferencing can be IMHO done only inside [COLOR=rgb(39,42,52)]reference_loot_template.
In the other loot_template tables the worst thing you can do is making a loop.
So I think the wiki text isn’t correct and describe the situation last year before changing a lot of stuff in loot tables.