I tried this with Warwick. His ult doesn't give stacks, so you have to make 4 Autoattacks afterwards to get Guinsoos Rage.
That is non-transparent design. Warwicks ult procs on hit effects. Autoattacks give a stack for Guinsoos Rage. So there has to be a special rule here, but you can't read this rule anywhere.
Please make the game more clear with less exception rules, or at least mention them.