Yeah, mix recall served as a massive test matrix for all kinds of operations flipping in and deleting fx, envelopes etc.
Lots of old bugs with automation instrument tracks and take lanes etc got squashed as a result.
Regarding load time, its very fast if there are no fx being recalled as Seth mentioned. With fx its dependent on the fx itself. If you mix recall a sampler of course it will take some time to recall (yes mix recall also recalls synth settings for all referenced tracks)