uncoupling membrane - Tile Advice

[On one]

Hi All
Can anyone verify some advice given by 2 insulated board companies that...
when laying insulated boards(wether onto concrete or by overboarding timber floors)then laying ufh,slc then fitting natural stone that you don't have to fit an uncoupling membrane? The advice given is that the insulated boards act as an uncoupling membrane!
Any advice please!

 

[DHTiling]

They will in a way but not a full on anti crack and if i use marmox etc then i don't uncouple.

 

[On one]

Marmox was one of the tech dept i did ask,just a bit surprised about the advice,given that there is (electric) ufh between the boards and the stone.

 

[White Room]

What stone is it......

 

[DHTiling]

Marmox was one of the tech dept i did ask,just a bit surprised about the advice,given that there is (electric) ufh between the boards and the stone.

You will need more movement than there should be to crack right through a marmox board...

 

[On one]

What stone is it......

Don't know!!!! I am estimating this one blind at the minute from a plumbers scaled drawing.

 

[White Room]

I wanna know what stone it is as well....