It‘s not only that, Firefox also forces you to use the Developer edition (which updates about daily, FORCING you to restart it) if you want to install extensions that aren’t signed by Mozilla (e.g. your own).
This behavior reminds of Apple. They say it‘s for security (where have I heard that before), yet Chrome doesn’t seem to need such a restriction.
To me it seems like another step in many of Mozilla‘s enshittification.
You don't have to use the developer edition to run unsigned addons; you can use the ESR version or nightly as well.
I am pretty sure Chrome has also added the forced restart for a bit now. It might not show up right after the update, but it doesn't take long. I don't remember if it was straighforward, or just crashed new tabs.