Nicely put :hat:- and I totally agree about the diversity in the community for us each having our own preferred processes that we know and love :-)
If I understand correctly, it seems to me that the key feature of this particular immersion chiller in question is that it is very long (I've seen 23m quoted in one of the links). So for them to claim it's substantial faster than a counterflow, they'd have to be comparing it to one about the same length - which would be a bit of a beast (!) but it would work very very fast.
Forgive me for getting geeky for a minute - this isn't because I'm trying to show off or say I'm right (!!) it's just to add a bit of context
There are two reasons a counterflow chiller is interesting:
The first is that the whole volume of the hot wort comes into contact with the cooled surface of the pipe walls for the same period of time, because it all flows through the tube. In contrast an immersion has to be agitated quite vigorously during use, otherwise different parts of the wort spend different periods of time in contact with the chiller pipe.The second is that the counterflow is extremely thermodynamically efficient at how it utilises the temperature difference between the hot wort and the cold tapwater in order to transfer heat energy out of the wort. This is because the fluids are going in opposite directions (the 'counter' flow thing) which means that the temperature difference is maximised at the end of the process, so that the wort just emerging from the end of the device benefits from the maximum 'cooling effect' of the fresh water going in (see here for more details: Why counter flow heat exchangers are more efficient).
Again, thanks for the information TETB! Lots to take away from this chat....