This seems to be the norm with most updating software, and it drives me nuts. I use Aurora Store to download and update Google Play apps, and it’s the same thing – no updates, then I’ll check again and there’s a full list. Same thing in Windows updates, same thing in Linux Mint.
If there’s something going on in the background that takes 5 - 10 minutes to complete, then at least the app should be honest about that and say something like “this can take some time” rather than a definite “no updates available,” but I’ve just mentally started interpreting it this way.