std::ranges::join_view::iterator's hidden friend iter_swap is specified in [range.join.iterator]/16 as:

friend constexpr void iter_swap(const iterator& x, const iterator& y)
  noexcept(noexcept(ranges::iter_swap(x.inner_, y.inner_)));

-16- Effects: Equivalent to: return ranges::iter_swap(x.inner_, y.inner_);

Notably, the expression ranges::iter_swap(meow, woof) is not valid for all iterators meow and woof, or even all input iterators of the same type as is the case here. This iter_swap overload should be constrained to require the type of iterator::inner_ (iterator_t<range_reference_t<maybe-const<Const, V>>>) to satisfy indirectly_swappable. Notably this is already the case for iter_swap friends of every other iterator adaptor in the Standard Library (reverse_iterator, move_iterator, common_iterator, counted_iterator, filter_view::iterator, transform_view::iterator, and split_view::inner-iterator). The omission for join_view::iterator seems to have simply been an oversight.