This would not surprise me.
I have a 2009 MBP with 4G RAM. Performance issues become very obvious with low spec hardware. Safari is incredibly snappy, complex pages like amazon.com scroll smoothly with no effort. This old machine actually feels new in that scenario.
The only concern I have about Safari is that Apple's security patches seem to come at a slow pace.
Lets not forget that it was Google that forked WebKit resulting in duplicated effort to implement various features. Google also loves to ship stuff that isn't actually standardized yet (which is fine) but today's web developers go whine about Safari not supporting it yet. No shit Sherlock, it's your own myopic view.
Only testing in Chrome is as bad as only testing in IE 6 in 2006.
You may want to avoid that blanket statements around developers who've worked with indexeddb, safari's implementation is famously awful, so much so that caniuse makes special note of it.
Assuming we’re still talking about mobile Safari on iOS here, unfortunately that isn’t true in all areas. For example, the way iOS Safari handles HTML5 media elements is essentially to play them through a plug-in. We had to implement a whole new authentication mechanism for a site I work on that serves video content to logged in users, because it wasn’t actually Safari requesting the video resource so we weren’t seeing the user’s ID cookie. There are numerous other problems with how iOS Safari handles video content that make it difficult or impossible to implement other functionality or UI behaviour that would make our site better for our users.