My reading of the following
.Planning minima for a:
destination alternate aerodrome, or
isolated aerodrome, or
3 % ERA aerodrome, or
en-route alternate aerodrome required at the planning stage
is that it is saying that it is a destination alternate OR isolated aerodrome OR 3% ERA OR en-route alternate…………..required at the planning stage not that it is en-route alternate aerodrome required at the planning stage. ie If you need any of the above, so if you are non ETOPs then the en-route alternate is not required.
If an adequate aerodrome has the wx minimum required it becomes a suitable aerodrome. They are stipulating weather is required +- 1 hr therefore it is suitable.