The seven-time world champion, whose Mercedes team won eight constructors' titles in a row from 2014-21, said on Thursday Red Bull's dominance was such that they could stop developing their current car already to focus on 2024.
"I think the (governing) FIA should probably put a time when everyone is allowed to start developing next year's car. Say August 1st," Hamilton had said.
"Well, he’s obviously talking from personal experience," said Horner, whose team are unbeaten this year and chasing a 10th successive victory, at the Austrian Grand Prix in Spielberg.
"I think it would be an incredibly hard thing to police.
"How an earth could you say, right, first of all, just go. How do you prevent people thinking about, or working on, next year’s cars?," he added.
Horner said the existing reduction in wind tunnel time, which meant the most successful teams had far less than those at the back of the grid, already acted as an effective handicap system coupled with budget cap restraints.
Stable regulations, with the next big change scheduled for 2026, would also help rivals to close the gap.
"The most important thing, and the history of Formula One demonstrates it, is stability. Not messing with the regulations will always create convergence. I think it’s just a period of time before... you can see that convergence is already starting to happen," said Horner.
"I think by the time we get to the end of '25, probably all the teams will be very converged and then we screw it all up and go again in '26."
