But would it allow us to identify scams and phishing pages more easily, with knowledge of what the platform is supposed to do?
Well, a phishing site can just show a similar page, no need to copy or pretend functionality. So there it would not help; the original site needs be smart in order to make phishers' life harder.
Scams? Just see the cloud mining sites that show pictures of actual hardware and show some random numbers for hash rate and income and people fall for that; exchanges with fake orders can probably also be made, but why, the effort looks big imho.
Selective scams? Yes, those still happen and maybe there some knowledge would help to identify them fast. But also a public copy of an existing exchange would even make the scammers' life easier.
Scrutiny? If I'd have my exchange and have my code public, I would internally use at very least a
modified version of that, for my own business' security.
Overall maybe I lack imagination, but I find somewhat debatable the usefulness for the average Joe of such code becoming public.