Sure, ifError rejects, but I don't think the behavior here is surprising or strange at all. This is exactly how one would want it to work. If you wanted to await it, you could do that.
Is the concern you're raising that people may accidentally orphan floating promises? That can be addressed with linter rules. [1][2]
Yes, but the floating isn't the issue: throwing in my example was just a concrete stand in for promise side effects in general. Running queries you only need in one not so common branch before the conditional gets checked, for instance.
Tell that to my junior coworkers. It's probably the single most common cause of async bugs in our codebase.