It's not a complete wash for the TSA, especially as the TSA ought to know well enough that anything that makes the TSA way more of a revenue center for the government makes it less likely to be under as much pressure to cut costs over the longer term.

Where did Congress define "one-way" or "round-trip" in the creative way that the TSA is using in order to further tax passengers? If anything, the TSA seems to be trying to be more loyal than the (legislative) king without restricting itself to what the (legislative) king actually wrote down.