The idea of some legal requirement in public lands to put in at only designated launch sites (outside of state or national parks) is completely foreign to me. Is that really a thing?
There are many designated launch sites along the rivers (at least near me) that are not maintained by the state (and, the way the law is written, only those maintained by the state require permits).
For example, moving downstream, there is a launch on the Conemaugh River in Johnstown that is maintained by the City of Johnstown, another in Seward that is maintained by the Conemaugh Valley Conservancy, one in Blairsville maintained by the boro, one at the Conemaugh Dam (Army Corps of Engineers), one below the dam (Indiana County Parks), one in Saltsburg (boro), etc.
None of these are state-maintained so none require permits. There IS one (on the standing pool) between Blairsville & the dam where a permit may be required because the land is owned by the Army Corps but leased to the PA Game Commission.
Again, no big deal to paddle here without permits if you're willing to see who owns / maintains the launch. Then again, the safest way (if you're into such things) is to buy the permits, stick 'em to you hull and trust that a heat gun will remove them when you're tired of seeing them (it probably will).