Why can't I use Electrum seed to recover my wallet on Trezor and Blockchain.info?
Electrum uses a custom mnemonic format so yes Electrum wallets cannot be restored in any other wallet using the seed mnemonic. Instead I suggest installing and running electron cash to get access to your BCH straight away. It's a fork of electrum for bitcoin cash and by default it imports all your electrum wallets automatically. The official site is https://electroncash.org/