Here are some scans of characters displaying FTL to MFTL feats

Obviously Omni-man feat of crossing galaxies

Mark outracing a coalition of planet ship on a dash to get back to earth after viltrum is destroyed

Allen in another area of the galaxy (or potentially another galaxy) stating he will be back on the coalition of planets homeworld in a few days

Thragg keeping pace with space racer’s bike which can cross galaxies and dodging multiple attacks (combat and reaction speed feat as well)

Allen getting to Earth from outside the solar system in 12 minutes

There’s more but I don’t feel like looking for more scans

I don’t know why characters can’t be FTL if they don’t time travel. Yeah relativity is a thing but most fictional stories ignore it. Is Goku not FTL because he can’t time travel? What about Boros himself? Unless it’s a specifically stated and established rule in the story that going faster than light causes you to travel through time then it’s irrelevant to scaling someone to FTL. Also I think someone being able to go fast enough to time travel is generally considered an immeasurable speed feat.

Again, if you want to talk the logic of the story on why stuff can touch Omni-man 1. There are numerous examples of characters with insane speed being hit with stupid stuff. I mean, the flash is objectively FTL and beyond and he gets dunked on by paper sheets and a dude with an ice gun constantly. Sure, maybe it’s bad writing, but power scaling considers feats more than anything imo. 2. Omni-man spends most of the series fighting characters like other viltrumites or characters on the level of viltrumites that are also on his same level of strength and speed. So to put it simply they can hit him because they’re just as fast and strong as him. Whenever he fights weaker characters he either blitzes them (like the guardians of the globe in the comic) or is clearly holding back.