Pro Flo 4 Timing

I note that ‘Bite Me’ on the Edelbrock forum is now putting it down to timing chain slackness and the need to run a tensioner. I replied by stating that if that’s the case then phasing of the rotor should be no benefit.
I still suspect that the different, narrower rotor they use on SBM’s is really the culprit, I’ve asked why they choose to use this on SBM’s.