You will be more effective if you deploy your words more carefully.
Loose coupling vs tight coupling has an established meaning ≈ “if a change to module X causes a failure in module Y, then we say X and Y are tightly coupled.” This has some “knock-on” effects that you are trying to gesture at, like, “If two modules are tightly coupled then because of that tight coupling we usually have to coordinate deployments between them both.” And then you're like “I can ship new CSS without having to coordinate a deployment of HTML, that must be loose coupling then!”
But this is a sloppy way to use the language, because in the one case you have one module, and in the other case you have two: there is no coupling in the Tailwind case because there is nothing to be coupled because it all ships as one module, then you construct a more modular approach, one with two modules in fact, and these modules are (depending on how you squint at it given that we are doing decorative programming and there are no explicit errors) in fact “tightly coupled”—the semantic HTML essentially provides a customized API which the CSS uses by hooking into; this is a common form of tight coupling in microservice deployments for example.[1]
So you are actually looking at, one module plus a static asset that defines a common language, vs. two modules that are tightly coupled, and declaring that the two modules are “more loosely coupled” and this is somewhat of a nonsense thing to say. Like I get what you were going for, I didn't write this as a top level complaint because I understand what you meant, but here in the thicket of comments I see that you are not communicating well with your interlocutor because of this sloppiness and language, you might want to pivot?
[1] This point about microservices is likely to outrage a random passerby, look I am sure that your microservices use RPCs against HTTP APIs in a way that doesn't cause you much grief in having to update multiple modules in one commit (if monorepo) or stage “topics” (Gerrit’s term) where you carefully have to merge 2 or 3 pull requests to different repositories all at the same time (if multi-repo). But even though your microservices are loosely coupled, I have worked on very similar architectures where we did have to stage topics and if you didn't then changes to service X would break service Y, “We’ll ship a new value for this enum, that requires changing the common schema repo, which requires updating every microservice that looks at that enum so that it doesn't have a deserialization failure ‘this is not an allowed value for that enum’ when the new values start rolling out, the ones that actually switch() or if() on that enum need to be updated to do the right thing, oh, I missed one because it relies on the contract that if enum == x then fieldA is set but if enum == y or z then fieldB is set but now when enum == q neither fieldA nor fieldB is set...” and I am happy that you haven't had these problems but yeah, some microservices are tightly coupled by this definition.