When I won a cryptosteel in a raffle here on the forum, I learned that all I needed was the initial 4 letters and everything would be fine
It wasn't until I used it and was sure it worked that I was reassured and learned more about the BIP39 in that sense
A healthy habit I now have is to check the seed immediately after backing it up somewhere. On my airgapped computer I do a simulation by restoring the wallet using the backup and checking if the addresses match. This way I am ensured that if I ever really need to restore my wallet, it will work.