A Monero private key is any 256 bit number mod l and the seed phrase is deterministically derived from this private key. 24 words (the 25th is a checksum), from the dictionary in Monero, gives enough bits (257) to encode/decode from the 253 bit random private key.
As noted, the Trezor Model T uses a 12 word phrase with a dictionary which is only good enough for 128 bits (plus a checksum). This essentially limits the possible range of private keys.
Longer bit ranges are of course more desirable.
It's worth pointing out that both Trezor devices can be initialized with longer phrases [source]:
Note For advanced users: It is possible to generate 12, 18 or 24-word
seeds on both Trezor devices. If you want to generate recovery seed
with different length than default (e.g., 24 words on Trezor Model T),
please see initialize device with trezorctl command.
Generating 24 words will give enough range to cover all possible Monero private keys.