The results in your comment aren't measuring the same thing. There's no grep on the /tmp/all.log in the middle code block, which is the thing they're talking about comparing.
My second operation is covering that. The reason my results show better is because they are counting the decompression against journalctl. It is doing a decompression operation and reading while grep and rg are just reading.
Btw, you can choose not to store journald files as compressed.
Where exactly did you test the speed of "grep sshd /tmp/all.log"? The entire point of their argument is that's what's orders of magnitude faster than anything journalctl.
The results in your comment aren't measuring the same thing. There's no grep on the /tmp/all.log in the middle code block, which is the thing they're talking about comparing.