Can you explain the apparent contradiction in your statements?
Ubastet was released on June 1, which is about 2.5 weeks ago, yet taransworld is saying it is in chests now. Sirrian’s release notes for Ubastet don’t make any reference to the usual 3-4 week waiting period, only the 7 day exclusive period.
I think the waiting period may not apply for mythics as it does for most other troops.
Edit: after checking some older posts and the GOW events spreadsheet, it seems as though mythics go right into the drop pool after their exclusive week ends.