Honestly I've only come across it once reading the MDN doc page on JS classes. I understood classes, when they first released for JS, to do nothing really different from objects. Well they allow constructors and stuff, but it was never on par with how they behave in other languages. So yeah, not a fan of classes in JS, and I saw the term as a demeaning way to refer to the feature. Marek really nailed it, but I don't see it that often.
If this is bothering you, maybe you're reading too much? That can be a problem for audodidactic learning. Sometimes you can be on the 'learn' path too much. Try making stuff rather than reading what people talk about.
As far as it being a canonical term, I don't really think it's one to bother yourself over. I've been starting a personal list of terms that I find much more valuable than syntactical sugar.
ps: imo actually using the term 'syntactical sugar' is as dull as saying any particular piece of software works by magic, or even appears to work by magic. So you have my vote for 'please stop saying syntactical sugar'. It's like 'plox', I'll never say it! It's 'plz' and only 'plz'!
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.