* background sync is not a web standard, it's experimental chrome tech (though it's been submitted to the WICG)
* I can only assume "proper offline" refers to service workers which is a WD with partial support (in the browsers in which it's implemented, which exclude Edge and webkit), webkit has it listed as "under consideration" and the last spec revision landed around the time of the last major safari update (mid-2015)
* notifications is fair, note that desktop Safari supports and that there's almost no mobile support at this point (also not supported yet in Edge)
* indexeddb is fair wrt current standards, but does not support "apple hates webapps" considering safari supports websql
* rtc is fair, and in development
* filesystem is proprietary chrome tech, dropped from standard track
* media sinks is fair, a WD with incomplete support on chrome
* media session is in development everywhere except edge
All in all, as far as conspiracy theories your comments mostly support you being a chrome shill.