External Task Long Polling, conditions for more than 1 task returned

cc: @tasso94

Using async long polling for External tasks, what are the conditions for multiple tasks to be returned?

Given that long poll workers have established a delayed query, then query will return as soon as a single task is available. So generally is there any sort of grouping delay? Grouped by transaction? (if multiple tasks are generated as part of a single transaction?), multi-instance, signals and messages that correlate into multiple instances which have a external task as part of the transaction, etc?

cc @thorben
Thanks