Hmm...not the experience I'm having, the big dialog apparently hangs around in some cases. Keep in mind the first match found will not _always_ be a Replace/ReplaceAll, maybe that's the confusion here?
Let me restate the question: In a scenario where the first match found to the given Find text is _NOT_ a replace instance, what is the expected use of the "Replace in Files" dialog? Hitting "Replace"/"ReplaceAll" in that instance definitely is a problem (as either would do a replace on that first found entity). Or should the "Replace in Files" dialog not even hang around that long? If the latter, well, that's not what's happening here.
I've had SE exhibit the behavior you describe, where it switches to the second dialog, but that behavior seems to depend on the first match always receiving a "Replace" or "Replace All" response.
Can try to get a screencast later today or tomorrow, but really busy so cannot promise any sooner than EoD tomorrow.