The automatic updating of templates has been in the OS since 6.0 beta, and is not a defect. The point of it is that if an update comes down that requires new ports, variables etc that they get added in to the template with the update. (I've always had mixed feelings about it, and it would only have happened during a container update which never happens without user input one way or another.
The reason why you're seeing the FCP warning is because you've created a template that uses the same repository as something already within CA rather than installing and editing the existing template. Nothing wrong with that. FCP introduced that test because 80% of the maintainers either never filled out the URL or filled it out wrong. For the last few years, CA has automatically filled it out for everything present and ignores whatever the author chooses to put in there, and FCP by it's own nature is supposed to tell you about configuration mistakes etc and that test falls into it. FCP never actually changes anything... (But this test it does offer to change it because it was always a pain to have the user enter in the correct value)
The "workaround" is actually a by design thing. false signals to both the update system to not update the template, and signals to FCP to not generate any warning about wrong URLs and gives the user the option to avoid behaviour if they choose.