Need to confirm 100% whether someone can tell that a new wallet (with a new passphrase) on the exact same Trezor is related to the base non-passphrase wallet

Hypothetically, let's say I've only ever bought crypto P2P from a friend who was mining and selling. So, every single transaction has been non-KYC; no one knows I own crypto besides myself and my partner and we want to keep it that way.

Everything I've ever bought exists in 3 wallets on a single Trezor:

• Wallet 0 (shared wallet): 24 seed words (without passphrase)

• Wallet 1 (my wallet): same 24 seed words + "passphrase 1"

• Wallet 2 (partner's wallet): same 24 seed words + "passphrase 2"

Then, let's also say, for some reason the miner friend decides to stop mining and selling. So for the first time, I get to buy from a crypto exchange, i.e., KYC from now on.

If, after purchasing from the exchange, I move my coins to any of the 3 wallets above, the non-KYC coins (from the miner friend) will be compromised as they will be automatically linked to the KYC ones (the new ones from the exchange).

I think (please do correct me if I'm wrong), as far as the blockchain is concerned (i.e., anyone keeping an eye from the outside, basically) when you create a new wallet (with a new passphrase), there is no way for them to know if the newly created wallet is related to its parent/base wallet (the one without a passphrase). Meaning, these are 2 entirely irrelevant wallets, as far as anyone who keeps an eye is concerned, even though they share the same 24 seed words on the exact same Trezor, correct?

Now, let's say, in my case there are transactions between Wallets 0, 1, and 2, BUT, if I make 3 new ones on the exact same Trezor:

• Wallet 3 (shared / KYC): same 24 seed words + "passphrase 3"

• Wallet 4 (mine / KYC): same 24 seed words + "passphrase 4"

• Wallet 5 (partner's / KYC): same 24 seed words + "passphrase 5"

and at the same time, make sure there are no transactions between the new KYC ones (3, 4, 5) and the old non-KYC ones (0, 1, 2), then anyone keeping an eye from the outside has no way of knowing that the new KYC ones are related to old non-KYC ones, right?

TL;DR: Do I need 2 separate Trezors for KYC and non-KYC coins, or the exact same Trezor will do the job (given that KYC coins and non-KYC coins exist in different passphrase wallets of the same Trezor and there are no transactions between them)?