Triple world champion Max Verstappen took his 16th win of 2023 as Red Bull continues to rewrite the record books with its outstanding RB19.
The Mexico weekend marked one year since Red Bull was found in breach of the 2021 cost cap rules, which landed it a fine and a reduction on wind tunnel and CFD development.
That penalty came on top of the Milton Keynes team's success handicap as the reigning world champion, receiving the lowest development allocation of all teams as part of F1's Aerodynamic Testing Restrictions.
However, Red Bull maintained its advantage without carrying out major car developments in 2023, while rivals had to commission significant revamps.
But Horner claimed the full brunt of its handicap is yet to be felt, despite being able to focus most of the team's efforts on 2024.
"Certainly, you've not seen the full impact yet because it obviously has compromised the amount of development that we've been able to do this year," Horner said.
"Thankfully, we came out with a very strong car at the beginning of the year and we've been able to apply most of that development time, from quite early in the season, to next year's car. So, that's been important.
"With the wind tunnel restrictions that we've had, we've elected to use that on RB20, next year's car, as opposed to continuing development on RB19."
All 10 teams, including Red Bull, did comply with the budget cap for the 2022 season following a laborious audit process, which Horner felt had evolved in the right direction.
"It's a very complex set of regulations that has evolved and the degree of scrutiny this year was phenomenal, in terms of the rigour that the FIA went to," he explained.
"It was a full colonoscopy that we experienced during the summer. And I think that the FIA is learning as well.
"Of course, every company is structured in a slightly different way as well which adds to the complexity, whether you've got subsidiary accounts or what your reporting group is.
"I think the FIA has actually done a pretty decent job from what we've seen over the last 12 months."
Alpine's interim team boss Bruno Famin added that the FIA is actively helping the teams with how they report their expenses because it is "easy to make a mistake".
"We're working in Formula 1, Formula E, Le Mans and trying to assign the right expense to the right project is sometimes very difficult," the Frenchman added.
"The FIA is helping us to try to make it clear, as we are trying to help the FIA as well to improve their process because it's so complex that it's quite easy to make a mistake somewhere or to make a misinterpretation of what they want."
