Sorry, but you are being scammed. You are selecting for sales skills, not technical skills. Read what you've written. You're judging someone based on how they presents themselves - not anything about technical ability.
I have interviewed many people who are great at doing this impassioned sales speech, but are terrible at actual engineering. And in fact, many good engineers are not good at selling themselves in this way - they have spent most of their lives deep in code, not working on their social skills like normal people.
Why not actually test them similar to what they're going to be doing? If it's a sales or advocate role at your tech consultancy, well then sure, your approach works.