Four full octaves sounds about right for Freddy. Five is rare, Gillan had five full octaves. Laura Branigan also had five full octaves, but something about a certain higher voice that gets more appreciation, like Celine Dion's speculated six octave range. But I would make the same case with Mercury, he was very weak at lower pitch(not by comparison of other singers, but weak by comparison of his own range), like Dion. So if Mercury had that fifth octave, I'm not entirely sure I have ever heard him belt out anything at the lowest keys with the same power he can hit his highs.
So that's fine if we disagree. It's a fun chat.
At least we agree Burton Cummings is nowhere on that list of top tier singers.