Minecraft: 1.16.4
Forge: 35.1.36
Easy Steel: EasySteel-1.16.5-1.2.18

With this combo, ores that I set to false still generated. Dropping back down to the last 1.16.4 version of Easy Steel makes the config work correctly.

Yes, I do. I was creating a new world. When I saw the ore generated, I looked for a reason, downgraded, deleted the just created world, and created it again. Same seed.

Downgraded the version of easy steel. I downgraded from EasySteel-1.16.5-1.2.18 to EasySteel-1.16.4-1.2.14.jar. and this fixed the issue for me.

I tried:

Minecraft: 1.16.4
Forge: 35.1.36
Easy Steel: EasySteel-1.16.5-1.2.18

Disabled all ores in easy steel config and not a single easy steel ore was spawned.

Okay. Sorry. Must be something I did wrong.

you try it on 1.16.5?

No. I tried it as described. I'm using the Curseforge launcher and so far they have not added a 1.16.5 version of Forge to the launcher.

which ores did you disable in config?

All of them actually. I'm only using it for steel production. And in fairness, I didn't go hunting for other ores, and the one I saw on the surface was Cassiterite. Then I was looking for a solution and noticed the version number mismatch. I downgraded, deleted the world, restarted it and the Casserite was no longer there.

downgraded what?

you do know that disabling the ore inn the config only affects checks loaded after you disable it, correct?

It does not remove ores already spawned in loaded chunks.