[Gaffer]

Back when, my interpretation of the situation was that the IRS cannot collect the ‘penalty’ because it isn’t a tax, per se, even though CJ Roberts said it was so he could explain his (IMO) criminal duplicity.

What that meant, IIRC, they aren’t legally authorized to collect because it isn’t an income tax matter, but they can withhold any amount you are due as funds owed the government.

I honestly don’t know if this is still operative, however.

[Cboldt]

I think your take is correct. The only thing the law cut-off was collections. The money is due, the tax applies. But the IRS is precluded from garnishment and otherwise forcibly taking the funds.

I also think the amount of tax money at stake, that is actually "not paid," will be so small that there won't be any cases. The IRS won't even bother looking for the money.