FDA is always understaffed. This goes for field workers as well as reviewers. There is no way for the public to obtain the backlog of work that is piled up, and has been piling up for years.
BTW those approvals, I believe, are De novo only, and not 510K (those with predicate devices). The former take much longer (in BIELs case) because they are creating a new category of device, and a predicate for furture clearances.
The latter is much easier, as a predicate device is already cleared.