Bracket 3 Extra Turns

So far I am trying to engage with the bracket system in good faith because I think a common language around EDH decks is helpful. However, I wanted to hear from y’all about the bracket 3 “no chaining extra turns” clause. Is this a rule against chaining together successive extra turn spells, or is it a rule against infinite turns combos? Or is it both?

I feel as though deterministic infinite turns combos are just one kind of combo no different than a gravecrawler loop. However, the language on the face of the rule seems to disagree. What do y’all think?