Strange, for me this works just fine. If you’re at the end of the line, cursor after the link, and hit control-A, then type, does it still became part of the link?
It seems like this behaves differently depending on whether the link is at the start of the note, bizarrely – if I create a blank note, paste a link in, wait for it to grab the title, then hit ctrl-A (or cmd-left) and type, the new text becomes part of the link, but if I do the same thing at the end of an existing note it doesn’t.
There’s also some weird behaviour if you delete all note text and then immediately start typing again; if you make a new note, paste a link, wait for the title to appear, then cmd-A backspace and then immediately start typing, the new text is still a link, but if you wait ~10 seconds before typing again (or click in the empty textbox first) the new text does not become a link.