Really? They are still a draft? Chrome Dev and Chrome Canary already support it. It is not like them to change their minds on something like that.
Chrome is full of features that are not standard yet :)
It's common for browser vendors to start implementing notable features once they reach Stage 2 (IIRC) but keep them behind an experimental-features flag, to let developers play with them IRL and find gaps and edge cases in the spec. Then once the spec reaches Stage 3, sometimes the features come out from behind the flag for wider exposure, since Stage 3 means it's pretty much definitely going to be added to the spec, just maybe with a few more tweaks.
But things can still change until the feature reaches Stage 4, which means "accepted to be added to the next spec release". So I could see IDEs wanting to wait for Stage 4 before adding support, in case the syntax or any other relevant details change in the meantime.
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