do they specifically only tell us very little in their first news release about things so that later they can tell us more to keep us interested?

Yup, they usually like to tease some stuff, and then do preview articles until release. The Imperial Aces announcement releases a surprisingly large amount of info in the pack.

Yes they are deliberately minimal early on, mainly to keep us guessing. There is the slim (very slim) possibility that they are still developing some of the named pilots, but not likely.

That's the typical pattern of any business that announces something long before its actual release.

And I mean, it's worked hasn't it? Look at the many droves of threads and posts theorizing and probing that release just on this forum alone.

so when are they likely to release more info on the new ties?

I'd guess maybe 3-4 weeks for more info for Wave 4. At least that's how it was for Wave 3.