Obviously you can create multiple wallet addresses with one Trezor hardware wallet and just one seed phrase. However, I don't know if one seed phrase has more than one BTC address, if our Trezor hardware wallet has problems such as a dead screen or other problems, other BTC wallet addresses (not the main wallet in Trezor) can be accessed in other BIP39 wallets or not.
In my experience
https://bitcointalk.org/index.php?topic=5467802.0, I have 4 BTC wallet addresses in one trezzor with one seed phrase, because there was a problem with my trezor, I was forced to access it in the BIP39 wallet (I use a trust wallet here) where only my main BTC address appeared.
My advice is that if you want to create other addresses on a single hardware wallet, make sure to also create a phrase for each wallet address. This is done in anticipation as a backup so that the funds we store there can be accessed safely and well in all conditions.
You are confusing seed phrases with regular private keys because the latter kind of sensitive information can't have more than one address of each type. For example, from a single private key, you can generate a single public key, from which it is possible to get addresses of different formats (legacy uncompressed, legacy compressed, P2WSH, P2SH, etc.). If your wallet generates a different address from the same private key, you specify which format you want to get. But if it is impossible to tell the wallet what you want from it, you should switch to a more advanced wallet. In contrast to a private key, a seed phrase can generate a virtually unlimited number of addresses of any format you want: a single hardware wallet with one seed phrase and several passphrases allows for separating your funds into completely unrelated sets of Bitcoin addresses. Some wallets like Coldcard even allow for generating dozens of seed phrases from a single seed phase, but it is overkill for most users.