I read your linked HN comment too, but: "legitimate interest in" [1] a thing and actual "authority" to do a thing are not the same thing.
I feel like I'm being bamboozled here. The fcc.gov "Notice", and this HN post, seem like they're talking about substantially different proposals.
[0] "I’ve advocated for the FCC to require device manufacturers to support their devices with security updates for a reasonable amount of time"
[1] "...we think that the FCC has a legitimate interest in just about any vulnerability on a wireless device"