Perhaps I hadn't understood how to do that, but the triggers I compared (Slate Trigger2, UVI DrumReplacer) can play 8 layers per trigger detection.
Why is this a major feature to me: many of sample banks use separate tracks for one sound. Eg snare up, snare bottom, snare room, snare over head, ... Having one instance to trigger a snare and being able to layer all these samples is easier than adding n instances and encounter detector settings issues on each of them.
My 2 cents

Yo