Adding it for extra rise is purely as food for the yeasts as supposed to vital wheat gluten which is added to increase the gluten. So yes, both are used for extra rise for different reasons giving the bread a boost but coming from different angles.
Rye breads will always be a close crumb with poor rise yet they have a lot of enzymatic activity but the gluten is poor. Adding diastatic malt serves no purpose so only non diastatic malt for colour and flavour.
A lot of miller’s, in the USA particularly, already add some malt to their flours. In the UK flour is exactly what it says “on the tin” - flour. And if it’s fortefied with vitamins and minerals they will write that. If we want malted flour then we buy malt flour which is bread flour with some malted grains. So unlike the USA which sells flour often with a certain percentage of malt but still sold as “flour”, we buy flour or malt flour. That is what I’ve been told by friends in the USA but if anyone else sees this please confirm or correct!
So before you go adding malt make sure non has been added already by the miller.
If your breads rise well then no real reason to add it. If you want flavour then go for barley malt syrup which is non diastatic and used for flavour only. If your flour doesn’t have malt and needs a boost then this will nudge it in the right direction. But a little goes a long way. It’s important not to overdo it as it can make breads gummy. We’re talking mere tsp (give or take) for one loaf.