Having the exact same problem, thought I'd provide more info and answer your questions.
When I first click on the URL, it highlights everything. The second time I click it, those blue "brackets" on either end of the selected text used to adjust how much of the text is highlighted appear, along with "Cut/Copy" options. The third time I click, the brackets and "Cut/Copy" options disappear and all the text remains highlighted. And back and forth no matter how many times I click. As opposed to prior iOS, where clicking highlighted text would deselect it and drop an insertion point where I clicked.
Every once in a blue moon I apparently tap on what must be a magic pixel because it unselects the URL and creates an insertion point where I clicked on the URL. I'm unable to reliably replicate this.
It's the biggest problem with URLs that fill the whole bar, yes. If the URL is short I can tap all the way to the right to put an insertion point at the end and then relocate it where needed. If it's long I can tap all the way to the left.
I've tested it in other apps (Chrome browser URL and a note in Notes)—no, I can't create an insertion point in any other highlighted text, either. I have to click outside the highlighted text or at the beginning/end to force it to unhighlight first before it will let me add an insertion point in the middle.
If I press and hold the keyboard (on the space bar or otherwise), it deselects the text and moves the insertion point to the beginning of the previously-selected text, at which point it can be moved around via swiping the keyboard as per prior iOS.
That gets around the worst of the problem—the complete inability to alter the URL without deleting it completely—but it would be very convenient to be able to use one tap to the URL to deselect with the insertion point dropped where it needs to be, as used to be the case.