As far as I can tell, it's literally the only way I use pinned tabs (other than when I accidentally do navigate away on them due to the lack of enforcement). I have several pages I always want open (e.g. my email, a couple of messaging platforms, Spotify, the web portal for texting via my Android phone), and then I have some varying number of other tabs open that I use for anything else I'm currently using my browser for. I guess this is one of those things where everyone's preference is different, because to me, having a static set of pages I always want open is pretty much the ideal use case for a pinned tab. I can't really wrap my head around wanting to use them any other way; if they can navigate away, they're just like any other tab but harder to close, and I don't really have a use case for enforcing the minimum number of tabs to be larger than zero unless it's literally to force a specific page to always be open. I find it far more annoying to have to navigate a tab back to the state it was previously than to reopen a page from a tab I accidentally closed, so having an extra layer of protection on closing a tab isn't nearly as useful as if it also had that extra layer of protection on what the tab itself was showing.

edit: I don't see it as the browser second-guessing me as much as following what I'm already trying to do in the first place. I don't pin a tab if I don't actually want to keep that specific page open, and taking an action to preserve a state that I opted into isn't going around my specified intention, but following it.

Consider these thoughts:

1. Let's imagine I have pinned a dashboard url in my bank's website. After some time, I go back to it, it sees I've lost my session, redirects me to the login page, and bam, that login page open up in a random, un-pinned tab. How is that a good experience?? You might say I should pin the login url, but no, after login I always want to get to a specific dashboard page.

2. In my view, pinned tabs are not for specific urls; that is what the toolbar is for. Pinned tabs are, for me, simply a way to have the most important tabs you are working easily available. And that makes sense, because the set of tabs that are most important changes a lot from time to time. I frequently have hundreds, probably a thousand, tabs open. If I have to pin every single url I'd like to go back to, I'll quickly run out of room in no time.

So let's say depending on what I'm working in this month, suddenly I find myself using Github a lot, or Notion. Then it is far easier for me to open some of my pinned tab and just navigate to the new urls I want, rather that have to close each of them , then create new pinned tabs, and hope that if I click on something on the page that is minor, I will not be rudely pushed into another tab.

Summary: I think you are using pinned tabs for what the toolbar was designed for.