It seems like a very specific thing for a reporter to ask and find out about.
If you know what you're looking for in those, you can identify a lot of different phosphor configurations just by the particular shape of the RGB peaks - the older ones have a distinctive multi-peaked red emission that I've seen in various LED bulbs as well over the years.
I doubt Apple mentioned it to anyone. Applying a spectrometer to any new light emitting device is just the sort of thing some people enjoy doing.
They're officially just called "Posts" now. It's a hell of a downgrade from how distinctive the old terms were, no wonder people still call them Tweets.
Community Notes was also set to be called Birdwatch originally, continuing the bird pun theme.