Yes, exactly, it's a modern day poll tax and many people in power want such a thing.
Regrettably, it is not just people in power - the HP newsgroups had plenty of individual contributors that favored things like poll taxes, voting for property owners only, etc.
This might be UK bias, but I take "poll tax" to mean a fixed tax on each resident for community services (as opposed to say a tax based on the value of the residence), but has nothing to do with voting. See https://en.wikipedia.org/wiki/Poll_tax
It's not a poll tax — it is apparently an element of the amendment Florida's voters passed, which requires that felons fulfill all elements of their sentences.
It’s consistent with all of the bullshit that southern white people in power have used to suppress black voting since the end of reconstruction.
I think it has to do with the wording of the law passed by the voters. Someone else linked the exact verbiage, but it basically hinges on the wording around having "completed" their sentence. If part of that sentence was repaying money, then until they've paid it they haven't really completed their sentence.
That doesn't cover why the state can't keep track and report out who needs to pay what, of course.
For Florida politicians, it's a feature, not a bug.