Constituency changes are not very sensible
Leaving aside accusations of party bias, it's sensible to even out major numerical disparities between parliamentary constituencies.
But slavish adherence to plus or minus 5% of an average size does seem rather inflexible.
Not only could the creation of geographically large constituencies make some unworkable, but losing the link with local authority boundaries for the sake of numerical evenness will create extra workload for MPs.
It makes no sense.