I guess ethereum supply is not fixed, in fact I've always known that ethereum had an indefinite Total supply, I believe that explains why there are divergent figures when trying to get the total supply. I really don't know why the developers made it this way, but I ones read that it would be corrected in the ethereum 2.0 project.
I hope you're right, but I never heard of anything like this.
I'm pretty sure tho that if ethereum 2.0 won't cut total supply of eth its going to kill it in long term