Citation needed.
I worked with two languages that have exactly this same behavior (Clojure and Ruby), and both of them this is not the source of any bug that I can remember [1].
Also, I would argue that Clojure as a language is much more ergonomic thanks to `nil` being `falsey`, so this is all about the trade-offs between safety and ergonomics. Considering that, IMO, Clojure without nil being falsey would lose much more than Clojure being a more safe language, I really don't seem much problem.
[1]: well, there is one, where one of our internal tooling had this function called `assoc-if` that it would assoc a key to a map if truthy, however this also meant that when the key was of boolean type and false we would also not assoc this; but we eventually introduced `assoc-some` that does what you expect.