As a sketch that may well do the trick, but as a demonstration of drawing ability it's abysmal.
The thing that bites guy's ass is ridiculously sized if a lion was intended, and that front leg looks more human than animal (then again, he might be going for some mythological chimera-ish thing).
Overall, the drawing is confusing and I can't make out what many of the lines in the legs/ground area are supposed to represent.
Finally, this is not a casual doodle. Lines were drawn and refined several times over. If he was going for manierism or El Greco-ish stylization, fair enough, but still proves little about his ability to draw. If he was trying to achieve a render true to anatomy and perspective, I call fail.
I don't know whether Cézanne could draw or not, but I don't think this works as evidence that he could.