To further explain this post: What does Ign , Get or Hit mean when running an apt-get update? (of which I still believe this is Q&A is a duplicate..)
Recap:
Hit means apt checked the timestamps on the package lists (Release/InRelease* and Index files), those match and there are no changes.
Get means apt checked the timestamps on package lists (Release/InRelease* and Index files), there were changes and those will be downloaded.
So the first time you run sudo apt update, there are changes to the InRelease files for 3 of the 4 repositories (those returning Get in the first 4 lines), as well as the Index files for the underlying components (the last 12 lines).
However, the second time you run sudo apt update, it only Hits the InRelease files, meaning there are no changes to the underlying Index files.
Therefore, apt does not bother to check the underlying Index files again, because it knows there are no changes this time (since all InRelease files returned Hit).
This is further evident by the fact that none of the 12 last lines of the first run contains the focal repo. All subsequent Gets or Hits are from focal-security, focal-updates and focal-backports - only those 3 which returned a Get from the InRelease file.
*: The difference between Release and InRelease files: InRelease files are signed in-line while Release files should have an accompanying Release.gpg file.
