> To avoid the cost of updating the entire page, htmx only fetches a parent element and all of its children, but this runs into the problem that you must choose the common parent element for all the elements you want to update.

Not exactly, you can use Out-Of-Band updates, which means the server can arbitrarily choose to update specific elements outside the parent.

> So the author reaches the conclusion that htmx is not meant to be used for SPA style apps. It's meant to add a little bit of interactivity to otherwise static HTML.

Can you clarify where I seemed to have come to this conclusion, as this is not what I intended to express.

I think what OP mean to say is that he came to that conclusion. I did not draw that conclusion from reading the blog post. But rather that HTMX is a good tool, but it's not all sunshine and roses, some features takes some work to get working.