Proto aggregators act like aggregators but are not yet powerful.

They're wanna-be aggregators.

"Oh no, we're competing against this proto aggregator, and aggregators are unstoppable!"

"They're not an aggregator yet, just a wannabe one. There are lots of moves that can work to head them off. And there are lots of ways that they can be foiled in their path to becoming an aggregator, for example if they don't have a head and shoulders advantage over competitors."