This is not my experience. Just yesterday I had to debug an error in staging that had cropped up because erlang had changed its public API for ssh_file in OTP/23. Despite being three private libraries down (and in an obscure option, and being not well documented) I had the bug identified in 30 minutes and the patch rolled out on all three library levels in another hour.

The biggest help was IO.inspect, and then the next biggest was elixir_ls, which had used typespec analysis and highlighted the error for me in my ide.