You’re making a lot of assumptions about their intent. For all we know it could just be openings for smaller ships to reach the landing decks. Or they could be openings to capture asteroids. Who knows what the artist intended. Ultimately it’s all fantasy. If artists constrained themselves to known technology we wouldn’t have so many instances of unexpected life imitating art.

The technology depicted doesn't exist, and, in my mind, it goes fast as shit!

Actually, there is a drive concept called Bussard Ramjet, which relies upon scooping up hydrogen ions while the ship is moving at relativistic speeds. The intake is augmented with conical magnetic field to extend the range of the scoop. You don't need huge fuel tanks to power such engine either - collected ions are compacted to produce thermonuclear fusion which is used to propel the spacecraft.

However, I don't see sense in having more than one such intake. Maybe a second one for redundancy...

It's fun to discuss plausibility of some purely hypothetical design on an imaginary spaceship 😃

What are some sci-fi artists / visual artists who do get it right when it comes to portraying futuristic tech that's practically designed? I'm genuinely interested to know