EX cell skipping theory?

For a couple weeks in a row now, some of the cells closest to me have been entirely skipped; frustratingly, the ones I targeted more in that particular week. I had assumed that it was due to sub-threshold raid activity (which never made sense), but I came across a theory that if the designated gym to host the EX in a given cell has an ongoing raid at the time the wave goes out, the cell is skipped. The reason why ties into the 'invisible egg' theory: that an invisible EX raid egg is placed on top of all gyms at the time invites go out and only becomes visible to pass holders 1 hour before it hatches. Consequently, those gyms do not host any other raids between the wave of invites and Mewtwo hatching, as the presence of the invisible egg precludes any other raid eggs from spawning, and...if a raid is going on at what would have been the EX gym, an invisible egg can't be placed and no invites go out. Despite being some monumentally sh*tty programming, that theory is corroborated by a number of cell skips in our area in the past couple of weeks.

It's hard to prove conclusively that this theory is true, but has anyone observed evidence disproving it? If it is true, it adds another frustratingly random wrinkle to getting EX invites.