And it's still broken, because the "Paste and Go" feature doesn't work.
Common sense suggests "Paste and Go" would be equivalent to using "Paste" (which correctly inserts text from the clipboard at the cursor position) followed by "Go to the address in the Location Bar." But if you unselect the automatically selected URL, position the cursor within it, then use "paste and go", Firefox ignores the previous URL and simply tries to go to the text in the clipboard. This could potentially be a security risk by tricking people into visiting URLs they didn't intend to.
If they don't want to fix this, it should be renamed to "Clear, Paste, and Go", because that's what it actually does.
If there is one command called "Paste", and another command beginning with and commonly abbreviated to "Go", "Paste and Go" should be equivalent to using both in sequence. If it's impossible to make it act in the expected manner, and impossible to label it correctly, the only remaining option is to remove the feature.
most non-technical people treat urls mostly as blobs (which doesn't mean they don't understand it's consisted of parts, but that's irrelevant)
so the URL field is mostly operating one urls as a while
that's why if you click on it in difference to normal text it will always select the whole url, because most times most people will either copy that url or fully replace it
similar "Past and Go" also operates as the url as a whole, not text segments. So it pasts the new url to where the old url was and "goes" to the new website
additionally if you don't just replace an url but edit it a "do this edit and directly go without giving me a chance to double check it" functionality doesn't really have any reason to exist as its way too niche and people who do that likely anyway use keyboard shortkuts instead of the context menu
sure there probably could be a better name e.g. "Replace Tab and Go". Or they could not show it if you don't have all text selected.
But "Past and Go" isn't a description of functionality anymore but has become something like a slogan or special term. So neither renaming it nor changing behavior is really acceptable from a UX POV.
Common sense suggests "Paste and Go" would be equivalent to using "Paste" (which correctly inserts text from the clipboard at the cursor position) followed by "Go to the address in the Location Bar." But if you unselect the automatically selected URL, position the cursor within it, then use "paste and go", Firefox ignores the previous URL and simply tries to go to the text in the clipboard. This could potentially be a security risk by tricking people into visiting URLs they didn't intend to.
If they don't want to fix this, it should be renamed to "Clear, Paste, and Go", because that's what it actually does.