A complete client side code rewrite to get rid of something is pretty much married to it.

In a start-up? Absolutely not true. This is the first version. I would suspect, as many go that route, that the "website in a frame" is replaced by native. That's typically the direction everyone goes in until they're already an expert at a specific platform and want to start on one instead of multiple.

Stuff gets rewritten all the time when it makes sense to do so. That's rarely a big enough issue that you decide you'll never do it.