Yeah this is a nice workout series. For those doubters out there, the op, was a National Champion in the open water 10k. He probably has “some” ideas of merit.
I haven’t seen anyone post on this threat who would be a “doubter”. Both I and NordicSkier asked some questions about the goals (e.g. was this geared to triathletes and if so what distance). The OP promptly clarified some of the points. If we don’t ask, we will never improve our understanding. There are many national champions & high level swimmers out there and they have slightly different approaches. That doesn’t mean any of them would be wrong. But when Mattbk suggests that we should all just swim 4k at a slow pace, he’s not helping the discussion and obviously wants to just come across as an arrogant dick.
I typed it with a a winking face 
Relax dude… Then I added a serious comment. You are being an asshole. My joking slow 4k response was to nordicskier, because he was implying that triathlon requires special triathlete sets for swimming. I have provided insight and info…all you and nordic have done is bitch…
That’s unfair. I got your joke. I was not bitching either.
I don’t think the OP takes into account that triathletes bike and run and carry that fatigue during swim training.
As well triathletes race predominantly in a wetsuit doing front crawl only, in a pack of swimmers.
These factors change how to structure swim sets for a triathletes.
These swim sets are fine for getting swim fit. I think they could be tweaked to be a better fit in the context of a triathlon program.
My opinion… flame away.
Ok, sorry, I wasn’t sure of your intention at first. This OP is used to front crawl in a pack of swimmers. Read his bio…there is a link at the bottom of his posts. He is a swim coach who is a former 10K open water national champion! Swimming can support more intensity than biking or running. This has been hypothesized to have many reasons, which you can look up if interested.