We also feel like he is trying to reinventing the wheel.

Yes! it is hard to create the html email templates and would also be responsive as well. We as design agency in new york have a team of professionals and their core responsibility is Develop responsive email templates. Looking forward.

Yes, not the best approach.. For pixel perfect and clean sketch to html coding without junk, would prefer using a service like https://www.htmlpro.net/sketch-to-html/ - Seen they are best..