Yep, and as soon as you need non-local updates, the whole concept of HTML-over-the-wire starts breaking down. I really like this HN comment on this topic: https://news.ycombinator.com/item?id=38081174
https://htmx.org/extensions/multi-swap/
In that example, you'd just send partials for the card and cart elements and they'll both be swapped out.