To me, clown bursts are like the ones posted in the photo above. Little to no real transition between the cherry and yellow.
Be advised that some people will refer to any HCB as 'clownburst' but they are fools IMO. It's the OG bust finish for Les Pauls. The HCB from Sweetwater that you are considering is fantastic. If you end up pulling the trigger, rock it with pride.
Clown bursts are a thing of the 70s and 80s, aren't they? Maybe into the early '90s? None of the stuff in the last 25 years is a true clown burst like in that Zappa pic I don't think ... (could be wrong, though)