I believe this is similar to Bugs that were already known.
For Graveyard and Voodoo, fsr your opponent's slots are mirrored on to your own slots, so that if they kill a creature, but YOUR corresponding creature slot is full, then it won't show up, or if they freeze a creature opposite from their voodoo doll, then their weapon gets frozen as well.
It MIGHT be different, so I guess I should ask before I need to try and test it.
Do you remember the skeletons filling the field in that exact order? Or was it a bit different?
Cause possibly you were playing so that every turn, he ate a RoL in the lowest creature slot.
You fractal, play like 5 RoLs. He eats RoL in slot 1, his Skelly goes into slot 6, and then continues, but since he ate your slot 1,
the next skeleton starts appearing from there. Except he never ends up eating slot 5, because you fractal again.
Eventually his board is filled and when he eats, RoL slot 5 is still there, so the skeleton does not appear.
That's probably what happened, but if you remember differently, let me know and I can test if it IS just to do with the last slot.