Harris wondered why Ferguson chose now, after successor David Moyes' challenging start at Old Trafford, to reveal the approach.
"Why bring it out now?" Harris told Press Association Sport.
"They haven't started the season off particularly well. Maybe he's trying to upset the apple cart.
"If it was true, I'd have thought it would've leaked out before.
"It just seems strange now all of a sudden since he's retired it's come to light.
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