Yep, I had BTC on the wallet during the fork.

I have used my seed and recreated the wallet using my seed -> no BCC -> Problem
I have exported and imported my BTC private keys in Electron "manually" -> BCC show up -> Now it works

I am still confused why the one worked and not the other.

So somehow the BTC/BCC as per August 1st were on a private key that was not recreated using my seed but that was still included in my list of private keys in the Electrum wallet

So far my understanding of the seed has always been that it would (re-)create ALL private keys used in the past, now, and the future.
This seems not to be the case. It seems to recreate only the private keys that currently hold a balance.

Is this the correct interpretation of the difference between "keys created by the seed" vs. "list of private keys in Electrum"?

As well, any specific explanation about this "we do not trust Electron, so we move our Bitcoins around thing"?