Why is the other order "better"?

I don't think it's better, I just fixed it with minimal changes.

Why is it a "fix"? The end result is two constraints, it seems.

The constraint orders matter, they are different things, you can not

namespace std::ranges {
template<view V>
  requires forward_range<V>
class slide_view;

template<forward_range V>
  requires view<V>
class slide_view { };
}

I think you may have misunderstood my intention as I didn't mention more in the comments, sorry.

Because the order is relevant: https://godbolt.org/z/3MPrfeWq6. In this case, the fix orders the constraints like in its class synopsis and those of its iterator/sentinel pair.

Ah, ok, this is making the declarations consistent across the synopsis and the iterator/sentinel. Thanks.