ss used his keyboard to write :
Any thoughts on this or is it just marketing hype.

https://mixergy.co.uk/

A rather a lot of hype there I think.

They didn't develop stratification floating hot water on top of hot, it
is a fact of physics and has always happened. Hot fluids always rise
above cold ones and stratification will develop.

An heater element twin high level/ low level have been available for
years, giving a choice of how much water to keep hot.

I can understand the diffusion of cold into the tank entering at the
bottom, will have some merit. I can also see how being able to vary the
target temperature will also have merit, I included it in a management
system I designed some 30+ years ago.