Have you tested if this is actually working, because I didn't and I uninstalled Blue wallet during AOPP mess?
To make sure it's still working, I just tested it. It had been a long time since the last time I used bluewallet.
Below is the screenshot I took from bluewallet.
Bluewallet by default supports BIP39 that can't be converted from electrum seed format, so I don't understand how they can make differentiate from imported BIP39 and Electrum seed words.
If you enter a BIP39 seed phrase, it generates your BIP39 wallet.
If you enter a seed phrase generated by electrum and there's a used address in the wallet, it automatically detects that and creates same addresses as your electrum wallet.