some more info
to display the G to Y PTU ECAM indication, it is necessary to have the condition Y sys press
lower than G sys press by more than 200psi. This condition is not required for the display of the Y to G
PTU ECAM indication. So, as soon as the Y EDP is selected off, the PTU starts faster than expected
and therefore the Y sys press has no time to droop the pressure.
This is apparent in the ECAM logic manual