Could it be that you don't know what a cameo is?
Anyway, you could call it guest appearances instead, a crossover usually means the characters share a part of a story together.
Here they just share the same world and make brief appearances in the other's story.
Hence a cameo or guest appearance, not a crossover.
I fully understand the difference, and that's the point. Allow me to attempt to explain the subtle nuance that separates this one.
I first encountered the Battle of the Bands bathroom scene in Acting Lessons, where it is a scene of small significance for the character relationship between the 2 main female romantic interests (or between the leading lady and her BFF). It's a story event. Looked at from the position of playing Acting Lessons, then yes, the appearance of Nicky and Mei-Lin could be seen as cameo. But it is important to note that the scene was released in Acting Lessons first.
In Retrieving The Past, it is not just that some characters come over to make an appearance. It's the the entire scene is recreated and reexamined from another perspective to drive another story. That alone makes it a crossover, because
events don't make cameo appearances, only actors do. An event reappearing in another movie is always a crossover. That's simply how the definition works.
Mrs Pearson's appearance in RTP was a cameo. The reappearance of the entire Battle of the Bands event, used to drive 2 different stories is a crossover. Where it gets really subtle is that if Mrs. Pearson having new lingerie is acknowledged and used in Acting Lessons in a future episode, that will immediately upgrade the appearance from a cameo to a crossover.
Awsome
