... possible to play - say - a sustain patch, and then a legato transition
MassMover is describing a VI feature not available in "multitimbral" synths, since multitimbrality here would mean articulations acting independently. You have to decide if you really want the limitations imposed by "multitimbrality", because if you want that limitation, VI won't give it to you; it gives you options here instead of limitations. VSL has customers who value the ability to legato-transition out of different articulation; they aren't about to abandon those customers in order to gratify one guy requesting vintage "multimbrality". Of course, you can still get the VI articulations you want by setting MIDI channel in Logic, which is a separate issue, despite your conflation.