Hello, when I use the Fine bar to select files by typing e.g. m, m, m to go through all files starting with m, then those files will be selected but Viewer Pane won't show their contents. Is this intentional?
Yes, otherwise it could delay things a lot if you landed on intermediate files which take a long time to load into the viewer.
If Find-As-You-Type is still open (hasn't timed out yet), push Esc to close it. Then push Space to load the file with focus into the viewer.
but it works with no issues when I simply press down arrow. There is no delay, it will simply not (fully) load in the Viewer/simply move on to the next file if I press down-arrow fast. I can't see the difference between "m . m . m" and down - down - down.
Or did I not understand what you meant?
It's just how it's designed.
There used to be a radio show decades ago, where they often did a radio skit/sketch with some absurd communications, and in the end the answer always was:
Frau Werwolf hat g'sagt es g'hört so!
Misses Werewolf said that's the way it's supposed to be!
People often use the cursor keys to move through a list of files in the viewer pane.
Typing to find a file by typing is often done for a different reason and the delays between keypresses may be longer, or the file you land on not of interest. It could work the same way but it doesn’t as the two things were designed with different situations in mind.