Primarily, I’ve observed behavior on Anki Versions 2.1.28-2.1.33 where new cards that have been buried (often for more than a single day) never become scheduled to learn as “new” on the first day they are available.
I have a parent deck (with 5 subdecks) that I use for “Learning”. Unlike other decks, the parameters on this deck are highly configured to force reviews in high frequency. New card steps are defined as follows:
1 5 10 20 30 45 60 90 120 180
Where the easy interval is 1 day, and graduating interval is 1 day. This entire parent deck and subdecks are all on the same learning group, which has a maximum interval of 2 days. The checkbox for “bury new cards until the next day” is selected. I add notes into this deck that generate 2 cards each. As such, when I review the first card, its siblings are all delayed to the next day. Additionally, for reviews, I also have related reviews buried till the next day, so this combination results in the sibling cards often being buried for 2-3 days until the first card has reached its deck-enforced 2 day [max] interval.
However, very often, the siblings do not become unburied on the first day they become unavailable, and are instead marked buried somehow:
Date of this picture: 2020-09-02
As seen in the picture, I created this note on August 30th, 2020. The first (top) card entered a 2-day interval on its last review on September 1st, making it due on September 3rd. Today is September 2nd, meaning the sibling card should have become available today to learn, but instead it has somehow been marked as buried despite no reviews having occurred today.