The worst you can do with DD-WRT is intentionally set a wrong country code.
Which lets you transmit on unauthorized frequencies, such as channel 14.
But you can hardly do that by accident.
Exactly, and plenty of closed source router firmwares expose the same option. And radios (Japanese radios can listen on German police frequencies, I think), etc. pp.; basically everything with an antenna that's sold in more than one country.
The same reason as other FCC regulations, so you don't inadvertently pollute part of the spectrum with either transmissions or noise? One device might not be a problem, but it's potentially a slippery slope with more and more software defined devices. It really shouldn't be that hard to come up with a solution either, even if it's just slightly more resilience.
The other solution might be to certify the firmware, so for instance it doesn't default to noncompliant settings when you flash, but that seem like a bigger mess.
> We were not, but we agree that the guidance we provide to manufacturers must be crystal-clear to avoid confusion.
Can you feel the wind off of that backpedaling?
There's no possible way they asked how devices were "protected" from "third-party firmware such as DD-WRT" while not expecting blocking of Open Source firmware modifications. It sounds a lot more like they got too much backlash: "...no, of course that's not what we meant [looks around nervously] you believe us, right?".
While this might result in a desirable outcome, I think it would have come across as far more genuine if they'd directly acknowledged that they originally suggested blocking all third-party firmware, and subsequently decided that they'd need a more nuanced approach. That, at least, would not come across as a (transparently bad) spin attempt.
Why does this need any kind of new change in the first place? The FCC can certainly go after people who actually transmit in violation of FCC regulations, and they do, no matter what device they use to do so.