Yup, either not enough coolant flow under demand, or airflow blockage.
Some of those electric fan shrouds are essentially a box that will block airflow at speed.
If you can try a faster pulley ratio and/or a shroud with flaps that open at speed, do so.
I'm assuming your lower hose isn't collapsing at speed, and there's no blockage elsewhere in the coolant flow.
Electric pumps usually move at one speed, if the hose was "collapsing" it'd do it whenever the pump was on.
The thing about electric pumps is this, they are designed for dragstrip use and in that application they can be useful. On a street driven ride it's just a problem waiting to happen.
