I could reproduce what can look as a discrepancy between the albums that are listed under a genre folder and the [All tracks] folder of that genre, but it has nothing to do with recently added tracks and is not new.
It happens for albums that have tracks in multiple genres.
For example, it you have an album that has 2 tracks with a track with genre "Pop" and the other track with genre "Rock", the
folder for genre "Pop" will list that album and if you enter that album all of its tracks are listed (regardless of their genre).
However, if you enter the [All tracks] folder of genre "Pop", only tracks that actually have genre "Pop" will be listed.
That can give the impression that tracks of the albums are missing, but they are of a different genre.