And Blink likewise removed support for non-V8. All the major browser engines are relatively tightly coupled to the JS engine at this point (not impossibly so, but there's definitely a tighter coupling than there was historically).
It would be easier to swap JS engines than other browser engine components probably, but yeah, not trivial. The patches to make WebKit support choice of JSC or V8 were janky in the first place and constrained what we could do.
