Alright, I'll spell it out for you: the behaviour may be what you'd expect from floating-point comparisons, but it doesn't have to be a floating point comparison in the first place.

No, it doesn't. Language designers make lots of decisions that end up being silly. But they make them. In PHP, if it looks like a number, it will get treated like a number when being compared via ==. It's a simple, well-established, fundamental rule.