I've never heard this rumor until now. For what it's worth, the old Mage Knight PAC had special abilities on it (like our powers) one of which was a ranged attack with a d6 to replace your damage. So maybe that's where the rumor started, I dunno.

The original WK figure gallery for HeroClix had little write ups on each character. The write up for Quasar mentioned his ability to deal 1d6 damage from range using RCE. Later, a designer revealed that RCE was originally 1d6 damage until late in the design of the game, but was removed when Probability Control was finalized.

That said, RCE was never 1d6 in any of the published rules. However, the original game was designed to be balanced with RCE 1d6 damage, most evident in Firelord and even Hawkeye.

Years ago at a Wizard World Con where I was a volunteer I met Hair10 who was the Rules Arbitrator at that time. I suggested to him a format where the rules would be governed for a figure by what the rules were when that figure's set came out.
Even back then he thought it would be next to impossible!
Since then there have been many changes as well as brand new mechanics.
It would be really funny to try though!

You can definitely choose one or two vintage rules for a specific tournament. Example, NAAT does not exist and you can use RCE and running shot together. The NAAT one is usually the easiest to remember and most fun to play.

I've done "retro" tournaments before where I do pick a few old rules, use those, and everything else is still current for simplicities sake. Much easier to keep track of than trying to use all older rules.

The most recent one I ran (about a year ago) had no Rule of 3, no FCCF, and no NAAT. Everything was the current standard.

Obviously it could be something fun to play, but I'm not sure you could ever use RCE and Running Shot together. In the original rules, RCE indicated it couldn't be used with any other power which would include Running Shot.