You don't have to believe the parts you made up. The comment you're replying to didn't actually state that a single customer was deploying to four different Debian versions. As written, the comment only requires you to believe that four Debian versions were in use collectively across the customer base.

So you say I am lying?

I'm saying they have much bigger problems than what python package manager they are using.

Granted, but that is relevant to the point I made in which way?

In reality you will have people running different OS versions. Maybe not within one org, but across users? For sure. If you are not using containers for one reason or another uv has shown to be a very good, reliable and easy to use way of dealing with the issues like these.

Additionally it has some other benefits when it comes to dev dependecies etc. Not that you couldn't somehow manage without it, it just makes certain things so much less pain as they were.