HMO plan doesn’t require a referral for a specialist, per the summary of benefits, am I missing anything?

I signed up for an Aetna HMO plan on the marketplace and was surprised that the summary of benefits says that no referral is needed for a specialist.

Before signing up for this plan, I did look up my eye (cornea) specialist using their NPI number on the Aetna website to make sure they are in network for this specific marketplace plan & took a screenshot. I made sure they are covered under the medical plan (there’s no vision coverage for glasses etc on this plan).

Does this mean I can really just make an appointment when it’s time for my specialist followup?

Do I have to establish care with an in-network PCP at all? (I won’t need a preventative care check up until next Dec since I just had my annual physical with my current PCP who is OON & don’t have any meds needing renewal or anything.)

Is being a current patient of a specialist enough to “prove” to the new insurance plan that the visit is medically necessary?

I will also call the insurance when I get my card to verify that the specialist is still in network before any appointment. I just feel like I must be missing something since it’s an HMO with a decent size network & I’m so used to needing to get and renew referrals to prove I need a specialist. Thank you!