The problem with that perception is that Air has become Apple’s branding for their consumer line in contrast to the Pro line. Apple tried to tempt people away to a pure “MacBook“ brand in 2015 with the 12” but through a combination of that being a weak offering and the strength of the Air brand, it failed to gain much of a following beyond a niche market.I've been using it for two weeks. I think it's a great machine. I wouldn't be asking myself if it's a bit too heavy if they'd named it MacBook rather than MacBook Air. After 13 years of using an Air, the name really doesn't fit.
Even on physical characteristics, the 15” Air is significantly lighter than any previous 15” Mac so there is a case for considering it to be light in a relative sense. And in an historical sense. These Airs are lighter than almost any previous Mac.
It is clearly in the same line as the 13” MacBook Air. It would be silly to call the 13” an Air but not to call the 15” an Air. Once Apple carried the Air branding forward in in the Apple Silicon models it was clear that they had committed to that. That would have been the time to change if they were going to.