In a technical directive that was originally drafted earlier this year but has recently been revised and put into force
Considering they are have properly defined halfway into the season it will be interesting to see how teams like Ferrari, red bull, merc, etc who were abusing this will be able to bring down costs
I think it was in the rules afaik. It was probably just the teams trying to use a different wording to use it. And the fia had to clarify it