It literally isn't. Did you even read the message the guy you're replying to, replied to?
The other dude said... "really hate this thing about artists doing various/tons of works at the same time and they just simply don't finish 'cause of time or lack of interest with the time"
He's saying that he hates when people have like 5 things they're working on at once, because certain ideas may be dropped, possibly in favor of others.
If D-art decides not to complete it, he doesn't have to. It could just be a random scene that popped into his head and he chose to do a little 3 second animation for it. Then, maybe, he gets an idea for a follow up 3 second scene. Then, maybe, JUST MAYBE, after that he says, "Eh, I think the idea may have ran it's course". So, he moves on. Nothing wrong with that, even if some might get blue balls from that choice.
And as others have stated, he doesn't get paid for his work. So it isn't a job. Call it a hobby if you want.
tldr: He doesn't have to turn every 3 second animation into an entire project for free. So, no, it's not his job.