There was no requirement that firmware be locked down.
The requirement was that consumer radio transmitters could be too easily made to use frequencies and power levels that violate FCC regulations.
If a device had a transmitter where firmware could control those things, and the firmware for the device was one blob that contained everything so letting the user replace firmware meant letting the user control those restricted parameters, then the manufacturer might have to lock the firmware.
There were other possible approaches. One would be to split the firmware into two parts. One part for the radio hardware and the other for everything else. Make it so the firmware update process only allows the manufacturer to supply the first part.
Isn't that a bit overreaching? I can make you a device the spews garbage on any wavelength you fancy, so they're really only preventing accidental radio pollution. Even in that case it's pretty unusual to prevent a consumer device (other than a radio) from being used in an unlawful way, Part 15 notwithstanding.
People were asking online for help dealing with WiFi interference, and were getting answers telling them how to install open source firmware on their WiFi routers, and giving them exact commands and configuration changes that would set the power higher than was legally allowed or stop them from avoiding channels that were being used by active weather radar (5 GHz WiFi shares channels with weather radar and is supposed to monitor and only use those channels when the radar is not in use).
I suppose you could call that accidental radio pollution, because most of the people doing it probably didn't realize that they were causing interference, but regardless it was becoming a problem.
Hence regulations to address it.
That's the world we're in now. You have a problem, you do a search online for help, and among the answers you often will find some that really should only be used by people with more experience or expertise than you but do not make that clear.
I believe the regulation applies to such a device you make as well, not specifically consumer Wi-Fi products. I.e. if you make a transmitting SDR it's not supposed to allow certain things.
The prevention all comes down to enforcement though, the law doesn't physically stop you from making a device it just means you could get in trouble for intentionally ignoring it and selling a lot of those devices.
You're totally right. I'm trying to make a moral argument, I think if it were unfeasible for an individual to make something (e.g. modern CPU) then you could make an argument for producers limiting them on the basis that it would effectively prevent anyone from doing the banned thing. The fact that it's roughly as easy to reflash an IoT device with custom firmware as it is to make an antenna that produces noise in a forbidden frequency means that you are adding a technical measure to prevent just some of that illegal action and not stopping a determined hacker.
I'm not claiming it wouldn't be an overall social good, but other areas of law and regulation don't seem to function like this (with notable exceptions like photocopying banknotes).
The (particular) law isn't actually aimed at stopping those who just want to go into their garage and produce illegal interference out of malice. E.g. people can create 200 Watt space heaters in their garage easily but it'd be odd to then conclude CPU regulations wouldn't stop people from doing bad things with CPUs.
That is to say, it's infeasible the average someone will make a working Wi-Fi radio which uses the Japanese channel 14 (involves changing what is sent by the radio, not just raising the frequency... unless you want to accurately re-adjust the frequency inside of your smartphone too) but it is reasonable to expect the average someone might just load some open firmware from the internet which allows them to set the channel to 14.
I will say I agree it's different than a lot of regulation. On the other thing I think that has more to do with radio space itself being very different than most things (i.e. a shared public resource) than inconsistency.
The requirement was that consumer radio transmitters could be too easily made to use frequencies and power levels that violate FCC regulations.
If a device had a transmitter where firmware could control those things, and the firmware for the device was one blob that contained everything so letting the user replace firmware meant letting the user control those restricted parameters, then the manufacturer might have to lock the firmware.
There were other possible approaches. One would be to split the firmware into two parts. One part for the radio hardware and the other for everything else. Make it so the firmware update process only allows the manufacturer to supply the first part.