"I have noted from the markings painted on the now closed road, that the road narrowing is minimal, enough to do away with the central refuge, which should never of course be used as a crossing as such. So losing this is technically not losing a crossing point. But narrowing the road should make the time a pedestrian spends off the footpath shorted, thus safer (in theory)"

er no, no, no, no, no and no (in practice).

This is a busy section of Perry Vale: traffic, cycles and people.
Forcing these non compatible groups into a smaller area means even less margin for error:
Carelessness will more likely result in the death penalty.

The council have sold a significant amount of carriage way here when they should have been buying. The pavement is far too narrow at the underpass and pedestrians often spill onto the road either side of the barriers at busy times.

Wider roads are safer for all, but presumably the council saw the chance to make some money.

They should make this diversion permanent.