Arguably, that would be misuse of the semantic meaning of "section." While <section> is nearly as generic as <div>, they should always have a heading of their own. The author's <swim-lane> already has a nested <section> with its own <h2>, but the <swim-lane> itself doesn't get (or need) its own even-higher heading.

And since that would drive us to <div>, I don't see any value in <div class="swim-lanes"> over <swim-lanes>.

It is unfortunate that you cannot simply move a block of HTML elsewhere where the context is otherwise perfectly suitable but expected heading level is different[0].

Section-relative headings were briefly part of the spec but quickly got removed. As it stands, I would not consider any block of HTML with an <hX> element portable.

[0] https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...

Web components come with additional complexity, heavy use of custom element definitions are more complicated to manage.

It’s more than just an aesthetic preference

But if you’re not really using web components it’s harmless but it’s a bit odd and pointless.