When I command-delete a song that played before the current song playing the current song keeps playing but the now playing highlighted song moves down one to the next track. Then it plays that track next, skipping one track in the playlist. It's happened on multiple albums with multiple tracks. Mac version 1.27.15.
In pic I deleted track 11 while track 12 was playing. You can see the song playing is still track 12 but the highlighted song moved down to track 13 and the next song which plays will be track 14 skipping track 13.