I guess this chapter was written just to bring Lum back into the main story. Whereas in the first chapter, she was pretty much treated as a one-shot character.
It's cool to see the nameless extras before they were morphed into Lum's Stormtroopers in the OG anime.
The Remake skipped this chapter (alongside many others) and I saw some complaints about pacing. IMO the Remake didn't really need to adapt this chapter because it didn't make sense for Lum to leave in the first place after she got "proposed" by Ataru.
Even if she left, she didn't need to be called back. She would've always come back if the writer planned the story with her in mind from the beginning. And in the Remake she does just that.