[support] How service files vs. version ranges works in reality

[mxr576]

It looks like on the first sight that services files vs. version supports works like usual semver constrains (like in composer.json). However, based on my testing it looks like

        "drush": {
            "services": {
                "drush.services.yml": "^10"
            }
        },

also makes Drush commands provided by a module supported on Drush 11 automatically. Is it correct? Is there a reason why ^ does not follow the same rules as elsewhere? As a contrib module developer it is important to understand this hidden* behavior because probably then always >=10.0.0 <11 constraints should be used if you would like to stay on the safe side.

re: hidden*: Only this line indicates to me that version constraints like ^ works differently here. Maybe that requires further, explicit clarification?

If a future Drush extension is written such that it only works with Drush 10 and later, then its entry would read "drush.services.yml": "^10", and Drush 9 would not load the extension's commands.