Sure, but in that situation a whale deemed the post to be worth an upvote. If the post has little value, no one with significant power will want to make it gain more visibility/payout than it already has. If it has been heavily promoted though, everyone should downvote it if its not worth its position on the page.
People seem to think that no harm is done by having a bad post being first on a page, just because they can't see the consequences. They don't want downvotes, but don't see that an upvote only system is negative for everyone who doesn't gain visibility (because its not visible). Everyone then goes about their day thinking everything is fine, because they're only exposed to that positive aspect. It's a mixture of Khaneman's "What you see is all the is" and survivorship bias. It's also a clear example of the Trolley problem, where people are willing to upvote a post to the detriment of everyone else, but not downvote one to the benefit of everyone else. This asymmetry just can't be good for the platform as a whole (centralization, unfair payouts, worse curation and content quality, etc).
Anyways, that second paragraph isn't directed at this post promotion issue. It's just the general human/community bias that's pushing against splitting downvotes from flagging. This additional exploit, no matter how weak it may be, is an additional argument in favor of downvote/flag splitting.