The UIWebView is an interesting example. They released significant performance advances in the iOS Safari web browser, but denied those features to developers of cross-platform apps on frameworks such as Cordova, artificially degrading the performance of Cordova apps compared to natively developed iOS apps. Both need to go through the AppStore anyway, but keeping as much dev lock-in as possible in terms of the tech used is obviously an interest here.
Add to that the fact that what positive feature development there has been in Safari (e.g. the above-mentioned excellent es6 support in the Technical Preview) has very specifically excluded the addition of any of the APIs that begin to blur the web/native divide (web notifications, userMedia, service workers, &c.)
But where does your example show, that they sabotage webstandards?
It shows what I said before, yes they control their system and making it harder for other implemations if they want ... but his is something completely different.
Add to that the fact that what positive feature development there has been in Safari (e.g. the above-mentioned excellent es6 support in the Technical Preview) has very specifically excluded the addition of any of the APIs that begin to blur the web/native divide (web notifications, userMedia, service workers, &c.)