What Parry actually says
He challenges the old assumption that technique must be drilled unopposed before it can be used in a game. The research doesn't support that neat sequence. Opposed practice should dominate, because it carries the real information a player has to read — opponents, space, pressure — and it teaches when to use a skill, not just how. If you do use unopposed work, keep a decision or some interference in it, and use it sparingly and on purpose.
Why I hold this line
Because I believe the thing we're really developing is decision-making, and execution comes with time and experience. A player who can do a move perfectly against nobody has learned a movement, not a football skill — they haven't learned when it's on. So I keep an opponent in almost everything, even if I have to make it a soft one. I'd rather my players be a little messier while learning to read the game than immaculate at a skill that vanishes the second a defender shows up.
The nuance I don't skip
I'm not a zealot about it. There's a place for unopposed work — a young player grooving a first-touch pattern, or someone rebuilding confidence with reps. Parry's point, and mine, is that it should be a deliberate small dose inside a mostly-opposed diet, not the default. Too much of it and you've built a team that's brilliant in training and lost in a match.