Ironically I'm a "implementation is 9/10ths of the law" believer, the proposals were PRs and working demos. Despite being a small start-up the team is not really into iterative development so much as lots of up-front planning and theory followed by big polished PRs.
I agree if I'm going to succeed I'll need to change my approach. I usually learn by doing and experimenting but it's tough to make incremental changes here to understand the codebase better