Just actual polyphony 
Right. If you touch plate 2, then touch plate 5 while still holding plate 2, the gate for step 2 will still be enabled, the CVs will be the ones from step 2, there won’t be any change in the keyboard gate output, the next reset will go to step 2, etc.
My expectation from more traditional keyboards is that playing legato would have switched the step gate and the CVs, but kept the gate output high… but I’m not sure what Buchla/Serge/etc. touch keyboards tend to do.
It’s not really a problem, just requires a bit more precision from your fingers if you’re used to using more of a hammer-on technique.