The animations in the Anim tab of the demo still lag a bit on my Samsung S6. It's always these subtle, uncanny things that tell you it's not a native app
Yes, you can usually tell webapps from native apps apart pretty quickly.
I have used a couple of native apps that crash on network problems, and in some cases they just vanish from the screen on crash without any OS dialog coming up.
I rather have to deal with mobile web apps than web widgets, specially if I have to code them.