This seems like the same issue/change I describe here (though I am using the v3 scheduler the v2 scheduler has the save difference form v1 as I understand it):
https://forums.ankiweb.net/t/v3-scheduler-parent-child-review-limits-and-deeply-nested-decks/12076/14
A workaround suggested to me was to use tags instead of sub decks but I don’t think that would work for your case of wanting one deck set to 0 reviews.
The only solution I can see at this time would be to downgrade to the v1 scheduler and I’m not even sure that is possible/easy to do unless you have a backup of your profile from before upgrading.