Because the FCC has to respect the first amendment
Most of us here will be surprised by things in Law School 101 (I know I have been, but only because it being phrased like this came up one time in a Legal Eagle), and many (like me) aren't American and don't get the meme-sphere of assumed knowledge about the FCC or whatever, so a broader ELI-15 might be helpful.
The FCC can't regulate the sites spreading misinformation, why would it be able to regulate the AIs that consume it?
De facto, or de jure?
Laws can change, and this is a mass produced consumer device with a single AI behind it (and for most people there's only Alexa, Google, Siri, and ChatGPT, with e.g. Cortana being in the "I didn't know they even did that" category) making it an easy target.
For example, I can say here on HN "fuckity shitting fuck shit" and not be fined or imprisoned. But try saying it to a judge during a trial, and the outcome will likely be different.
And it's the same for saying it on broadcast television at certain times of day and in certain contexts.
Misinformation is the same.
If alexa told people to drink bleach, lawyers would be queueing up to hit Bezos for restitution. And, if you read the story the programmers intervened.
My prior comment was a bit tangential and sort of off-topic, but I'll leave it there for context.
How is such a distinction useful?
I can, physically, drive a car over a speed limit, resulting in a fine; the fine is the enforcement of the prohibition. For speech (in the broader sense that includes non-vocal publication) we also have various prohibitions such as copyright and (as Musk has found) influencing stock prices, which are still prohibitions even if when they can only be enforced after the event.
Whether or not we should have such prohibitions/penalties specifically on AI models is something that I feel will be the defining political battle of the decade, and may yield different results in different polities: we already have very vocal cohorts who speak with anger of OpenAI "lobotomising" ChatGPT and "censoring" DALL•E (ditto Midjourney), while other vocal cohorts are appalled at the way even these models are being used to deceive, to sexualise, to propagandise, etc.
There are exceptions, but they're unlikely to cover something like who won the last election.