They don't work like that, they have no technical capabilites. I think it would work more like a company being ordered to pay a fine if a user on your instance finds out that his data is not deleted if he asks.

But this is complicated so I hope someone else has good input on this topic. Someone must have run a website with registered users in Europe before without being a corporation.

The fediverse brings a new touch to all of this also, since the posts and comments are replicated across instances. Will that matter to the EU law? Maybe, maybe not.