Kind of. You would make it harder to accidentally generate the same wallet.

But honestly, don't worry about it.

The chance to generate the same seed by accident is 1 divided by 2048^n where n is the amount of words you use since BIP39 has 2048 available words. [0]

So for example, if you use 24 words, it's once every 2048^12 = 2^11^24 = 2^264 attempts which is between 10^79 and 10^80.

For comparison, it is estimated that there are between 10^78 to 10^82 atoms in the known, observable universe. [1]

[0] https://github.com/bitcoin/bips/blob/master/bip-0039/english.txt#L2048 [1] https://www.universetoday.com/36302/atoms-in-the-universe/

Does that convince you to no worry about it?

Or at least convince you that this is not the use case for BIP 39 passphrases. Afaik, it's only meant for hidden/decoy wallets or for additional security in case someone finds your seed phrase.