I have tested with a multiple mycelium account wallet.
It will work for other accounts; however, you have to restore them individually. Meaning, follow the process outlined prior for each account within the wallet seed. You get a popup asking which account you want to restore.
https://talkimg.com/images/2023/11/15/F2MI2.png
My seed has 6 accounts. 0-5 I restored the first 4 as tests to know that it works.
I just created a 2nd account in Mycelium... then created a new wallet in Electrum, set the Options on the Seed input to "BIP39" and used the Mycelium seed... then on the BIP44 Account dialog, changed the 0 to a 1... and it created the same addresses as generated by 2nd account in Mycelium.
So it would appear you can indeed import multi-account Mycelium wallets into Electrum... you just have to split them all out in to separate Electrum wallets... a bit of a nuisance, but better than nothing!