I had the same experience at Amazon with their secret projects, including each iteration of their kindle fires
a) we have no idea if this is unique or not (hint: a Kindle Fire revision probably isn't)
b) it makes things seem more exciting.
The weird thing about Fuchsia is that all of the development is done in the open, but noone wants to give any context.
Btw: In February I spent some time looking at the then about 100 committers to Fuchsia/Flutter. Some quite impressive names. I think Fuchsia is a really serious effort in the Chrome team.
There's definitely a lot of ex-Chrome people there, but I don't think it follows that it is in any way in the Chrome team. I'm still curious as to why all of them are essentially creating a new OS, though! Quite the departure from what they've worked on before (and many have been working on the web for two decades).