I suspect you are absolutely right, Simon.

As to the radiator header tank welds splitting, is it possible that some form of cavitation is vibrating the coolant, resulting in fatigue fractures of the welds, and they think a swirl pot would remove the cavitation and protect the rad? I'm speculating: a well made aluminum radiator should be robust. So it the OEM radiator just "cheap" and not very robust?

Peter,
66, 2016 Porsche Boxster S
No longer driving Tarka, the 2014 Plus 8...