I think they knew full well what they were doing. It's undeniably goofy to anyone who's seen a horse. That right there ain't a horse. For one thing: it's egg-shaped and, for another; it's clearly about to get obliterated by the horse and rider on the left while brandishing an expression that reads "oh no I'm in for it now" like a Tom and Jerry cartoon.

This shit is hysterical and they knew it. Even if the artist had written out a confession of sincerity regarding their non-comedic intent I can't imagine holding that egg up to that artist and asking,

"You expect me to believe this is your best attempt at a horse? Seriously?"

without that artist at least cracking a grin.

The thing is, artists often don't have "make it realistic" as their primary objective.