If you got to that point it's just a formality, and unless you somehow blow it the job is (probably) already yours, if you decide you still want it. You seem to have jumped to unwarranted assumptions about the company culture; quite possibly the CEO does want to make sure the culture is good and remains good. It's not necessarily a binary test of whether the CEO can't trust delegating to their managers; it's also your constructive opportunity to use that conversation to get more insight into where the company, strategy, product/service, customers etc. are going. A good question to ask the CEO is about the broader impact of your role: that should get you some useful insight, also you compare the delta between what the CEO says vs what the senior managers said vs what the recruiter said; they don't need to be identical but they should broadly agree, and it shouldn't reveal any fundamental disagreements or ambiguities (e.g. "your role is incremental support of product X" vs "totally rewrite it in language Y in the next 9 months"). Listening to their response should also give you subtle behavioral cues about who in the company does/doesn't have influence, credibility and where the pain points are: you can't generally get that from the previous interviews, and it can be a faux pas to explicitly ask.

(PS: if you find reasons to suspect the CEO isn't delegating effectively to managers, then ask the CEO an open-ended question "How much do you do yourself vs which tasks do you delegate to your managers?" then listen carefully to their answer. And it's still not necessarily a red flag, it may just be a new or inexperienced CEO, or maybe overcompensating for one or two bad hire experiences at current or previous company. Compare to their answer to "How do you assess new hires within the first 90 days?").

The only (minor) negative I'd take from this is that it still behaves like a small startup scaling quickly, and they haven't yet figured out how to to scale interviewing and hiring for when they get larger... but that's overall a good complaint, it shows they're still growing. It's much better that your signoff interview is with the CXO (or VP) than the Director of HR, or an AI bot. Honestly I'd pay more attention to how many days/weeks/months it takes them to make the hiring decision than how many management layers were involved; that's a bigger tell of organizational dysfunction.

Don't overthink.