Here's a comparison including the big 3, ladybird, servo, and flow
https://wpt.fyi/results/?label=master&product=chrome&product...
To answer your question, yes. Apple requires 80% test passage of all the tests on web-platforms-test in order to be considered as a valid browser for iOS so they specifically targeted this suite to reach that milestone
It's a pretty silly requirement because wpt is not really meant to be representative of all web platform standards. It includes tests for non-standard features and the majority of tests are simple unicode glyph rendering tests.
I thought that no other browser engine could be provided on iOS. so no ladybird's engine, no servo, no gecko, no blink, only webkit
Some geographic regions have declared that not allowing other OS engines on iOS is anticompetitive so they're requiring Apple to allow them.
Apple is fighting it tooth and nail and coming up with requirements for other engines is a small way of doing that.
that was true until a few months ago due to a ruling in the EU. It's still currently the case that only WebKit can run on iOS but they're gearing up to change that