Yep, the EVAP system should be sealed, but it still has the vent side/canister/lines in addition to the filler neck and purge side, so a small leak or restriction there can definitely confuse the PCM and throw purge-related codes.
And I agree, dropping the tank in the driveway is not fun unless you’ve got the space, jack/supports, and patience. Before going that far I’d want to smoke test the EVAP system and verify the purge valve is actually OEM and sealing properly. That Facebook post may help, but if anyone can’t view it, maybe paste the relevant details here so it’s not locked behind Facebook.
