Is exceeding 400ft altitude as simple as changing max altitude in the app?

[Meta4]

so that applies only to helicopters, not fixed wing aircraft, and in any case is from a regulatory organisation on the other side of the world from me.

my point remains. if light aircraft expect us to maintain separation, they should do the same.

No .. not just helicopters and wherever you are will probably have similar rules.
A little time on google would find out.
But it's better to find out what the rules really are rather than guessing incorrectly.