Jess,
I've plugged and repaired hundreds of balls, some of them my own. The small area isn't large enough to worry about loss of reaction. Even the most talented and precise bowler is precise enough to release his ball the exact same every time.
Assuming the ball plug doesn't match the rest of the cover, we're more likely see a difference in reaction due to the "human element" than one tiny spot touching the lane once (assuming flare) on a part of the lane where there's typically no friction.
In theory your argument makes sense because of the potential difference in plug material used, but practically you'd have to be a throwbot on a C.A.T.S. to be able to tell the difference, if there is any. Just too many variables that the bowler can change in my opinion.
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Lane Carter, Strike Zone Pro Shops - Salt Lake City, Utah
Brunswick Amateur Staff