Not only is it not implicitly SPA behavior, as you say, good back button behavior design is actually hard in a app setting. And you can’t generally “get it right” — no matter what you do, in a sufficiently complex scenario (which… that’s why you built an SPA, right?) users will disagree about what the back button should do!

Generalized anti-SPA sentiment is silly. Saying “bad implementations correspond with SPA” is true but also silly because there’s not as much to get wrong in non-app settings which admit a “traditional” approach. It’s like the xkcd observation about heat maps and population density.