Users should have to explicitly select that they want to use a search engine. The options should allow a user to select "none" as a default for search engine, so that it has to be selected and so that the address bar is not improperly used for searches. This dual use of the address bar for location (URL) as well as searching can lead to security problems.
I don't actually know about it, the developers will tell for sure, but the algorithm that is quite defensive in terms of what it considers as a search query: for example I've only seen it search the input - when it was a single word: localhost. And in that case Firefox asked me if it was wrong to search it. Now it opens even localhost as an address.
I think, if you really want to open a url as an address without compromising it to a search engine, you can add http:// or https://.
But as a convenience feature.. If it's easy to implement..
Edit: a suggestion like on the first screenshot, but vice versa would fit perfectly (now it shows search as a second option if it thinks that it's an address, it doesn't show address as a second option if it thinks that it's a search query even though it's a valid url:
I know it's actually gateway.docker.internal, but Firefox knows this address too