Not being able to tell whether the app is installed is Apple's fault. Redirecting to the homepage rather than the specific link is not.

Being able to tell whether the app is installed sounds like a privacy violation. There is a mechanism for linking to apps in iOS; Google should be using it.

Actually it fires an intent, and if the application is there it will catch it, if not, it won't. No privacy violation needed as IIRC it won't communicate back to the website.

Could be wrong, haven't done much android programming.

It is possible to check if a URL scheme is valid, which helps to know if an app is installed that responds to that URL scheme.

I don't think it's possible to do this from JavaScript. (On the other hand, no real reason Google couldn't use a Smart App Banner, which is uncustomizable but presents an appropriate UI to either install or run the app.)

on android when I click this link I'm taken to my location search history on the web. I don't think this is apple's fault.

BS, web links can launch into apps, plenty already do it.