The date is probably something Jolla set and forgot to adjust later when they figured out payment schedule for later batches, or it comes automatically from Shopify. As far as I know, the final payment emails started coming out for the September batch.
You just have to wait patiently until Jolla contacts you. If it helps your anxiety, check the forums for people who have reported receiving the email and what group they are in.
Keep in mind that Jolla doesn’t send all the emails at once for the entire batch, so even if you’re in the September batch, it may take several days for the queue to hit the end of the batch.
I done this at least, ublock turned off, vpn turned etc. all the security/privacy things i turned off. Same behavior. It’s really strange behavior. An i’ve tried it with different browser too. opera, edge, chrome/chromium etc.