From my experience in silver, bad split-pushers are way more common than the 5v5 ARAM.

Problem is mostly people splitting when it's not appropriate for our teamcomp or their champion. For example, some games we have a really strong team-fighting composition but after a few won fights, my teammates get this idea that they can split-push when they actually lose 1v1's.

Alternatively the fed champion doesn't do well when splitting; for example I've had a few fed but immobile ADCs decide they're the split-pusher now, and we can't even take objectives when they promptly die, lol.

At the end of the day, can't really make generalizations about how games go down here. That would require people to know what they're doing. :')