@Opera-QA-Team Thank you. Before you posted, I filed a bug report: BS-103724. I supplied a quasi-example, showing what Opera put in and mentioning in the text what I had typed.
Definitely, just one letter will do it. It's one of those things where it was relatively seamless before and so I can't remember for sure how it worked. By my vague recollection is that as the typing started, Opera would insert something highlighted in the Address field, but if one kept typing the latter would be replaced by the user's text. If so, that's what is often not happening now.