IMO Improvistional Theatre is the only valid example here, the other 6 IMO are silent and I will explain why:
1. Music - Done mainly in ones own head, drawing on personal experience and skill to find something which fits with what you are hearing. The process may not be silent, but the creation is.
2. Stand up comedy - The writing/creation is done by the comedian alone, then when workshopping in front of a live audience they assessing the material against the reactions, and adjusting it in their brain silently. An audience reacting is not creating anything, it is informing the creative process going on in the brain.
3. Literature has editors and friends who read drafts - again all the creation is done in silence. Feedback may be given verbally, but that informs the creation, it is not part of it.
4. Product development - This is not artistic creation. It is commerical development. The initial idea and creation is most likely done by an inventor/designer on their own in silence. It is commercial requirements which push this into the further areas of development as you suggest.
I fully accept this is a subjective opinion so I am not stating you are wrong, only how other people can have different opinions based on perspective of what creation, the creative process, and indeed silence actually is.
You must have miscounted because I cant find another 2?