The FCC's initial knee-jerk reaction was very much along the lines of banning OpenWRT, and TP-Link subsequently deployed firmware to make it harder to put OpenWRT on their routers. Sure, they're now saying that it wasn't their intention and that they'll try to find a way to avoid it, but banning OpenWRT was and still is on the table and TP-Link and others have taken steps down that road.

As for the FCC rules: they still haven't put forth a clear explanation of how easy or hard the modifications have to be to get a router vendor in trouble. TP-Link's routers are still not fully secured, and just about everybody else still has routers on the market that are no more secure against modification than the TP-Link products. Absent any evidence of actual interference being traced to TP-Link products, it doesn't look like the FCC is merely being strict about enforcing their rules—it's more like they're making an example of TP-Link but deliberately withholding from a broader enforcement campaign while they and the industry try to figure out what to do (ie. can currently deployed hardware be made secure enough without locking it out of third-party firmware?). Meanwhile, the FCC is still having a chilling effect on open-source wireless router software and they still haven't provided any strong evidence that the harm is justified.