It's a good point, but I wonder if it is useful to still make the distinction between the two tags because there are probably questions relating specifically to the actual prototype developed compared (which fits the tag 'prototype') to the process of creating prototypes (which fits the tag 'prototyping').
This could also be the case with using the tag 'tests' to discuss different types of user testing as opposed to questions specifically relating to how to run a specific type of user test.
But I am interested in other people's thoughts on this.