Gm, the quorum of the key holders to your Bitcoin does not make something non-custodial. The only thing that matters is whether your explicit cooperation is necessary to move your Bitcoin.

As the saying goes: Not your keys, not your coins.

It's not: "Not your 3-of-5 multisig but your coins – oh maybe 5-of-7 but you can't really verify whether these 7 people are actually the same entity or not so it might be just a 1-of-1 because it's not your keys remember, but maybe they are an aggregated Schnorr signature which might use Musig2 (it's unclear to you) or maybe it's a Frost threshold signature you can't really say because they all look the same – but hey it's a multisig right and multisigs turn into non-custodial systems when they reach a magic threshold of 3 to 7 or maybe 50 it's kinda undefined."