Also, to answer your question, not it's not the same as a website because it will be a native Android app with the ability to communicate with the Android OS, like any other Android app.
The possibility of things — in terms of improved UX — that you can accomplish with instant apps are infinite. It all comes down to how you want to use it.
If I'm clicking on a link I want to open it with my browser, not with some app. I find this extremely annoying with facebook and even the news carousel already.
I can't open new tabs, copy the url, switch to other tabs like I would in the normal browser. This is extremely confusing and I don't how this benefits me in any way.
A better implementation would have been to have a popup with a list of compatible apps to run, including an option to run it in a browser like any normal link.
I really hope the NFC bit is opt-in by default. I don't want to have to manually disable it every time I get a new phone. In fact, even if I've opted into having the SF Park app run when I'm near a parking meter, I want the option to "reject" it just like I do when I get an incoming phone call.
Full OS access could mean permissions per page - could be awkward or ok. Much of the app vs. webpage debate here is the same as always - though offline advantage is gome.
Is there some point where websites start to significantly displace apps?
Yes. It happened about ten years ago.
I don't get the appeal, for example, of native apps for things like airlines, amazon, ebay, etc.
It seems to me that this is already slowly happening and this instant app thing is the reaction. After all, Google would lost the control if everybody started to use the browser.