I believe so, yes. Not sure on the exact timing but it’s the same month.
So for example, last month Miki got added to the ToL pool. I’m not sure if he was added to the HA pool on the SAME date or if he was added at the start of the month… or at the end of the month…
Give me a sec & I’ll check in Beta what’s the go if Grazul is added to the list now or not.
Edit:
Rushed thru some of the stuff in Beta & checked the HA10 pool (it shows it in a tool tip) and currently it has all old HotM up to & including Miki.
I’ll keep an eye on the pool at the time that ToL goes live to check if grazul is added then or not.
As a FYI to anyone reading this, you can check the pool at any time when you’ve built & researched HA10 as there is a little “info” button which shows the pool & odds of HA10 retraining.