I think you probably missed the beginning of that sentence, which was contrasting e.g. Bitcoin with the MimbleWimble approach.
The difference between 'both parties must be online at the same time' (true of, say, a phone call) and 'both parties must participate, even if it's during different weeks' is a substantive difference, I only wished to indicate that MW requires the latter, not the former.
The difference between 'both parties must be online at the same time' (true of, say, a phone call) and 'both parties must participate, even if it's during different weeks' is a substantive difference, I only wished to indicate that MW requires the latter, not the former.