Shortly after the race however, Renault lodged an official protest citing the legality of the floor on Grosjean's car.
Upheld, by the Monza stewards and Grosjean disqualified, Haas team boss subsequently accused Renault (and others) of being jealous and breaking an unwritten code by not warning the American team in advance - even though the FIA had effectively done this in issuing a technical directive (TD).
"We all look at each other's cars on a regular basis," he told Motorsport.com. "Us and I think quite a few other teams spotted a few races ago, because I think it was a floor that was introduced in Canada.
"It's true that there hasn't been a protest for a long time," he added. "But it's not a question of a gentleman's agreement or not a gentleman's agreement, they were given a number of races by the FIA to make that floor legal.
"We didn't have a problem with the time they were given," he insists. "But they didn't respect this time. I don't think they were really caught by surprise there.
"What I think Gunther is probably referring to is that if we spotted something illegal on a car, we wouldn't protest immediately, we would probably talk to the FIA or to a team before to sort it out.
"The TD was pretty public, wasn't it?" he added. "I think we were expecting like everybody else that they would come with a floor that complies with the technical regulations in Monza. We were surprised that they didn't."
Referring to the timing of the protest, he said: "After the race we gathered and we decided whether or not we were happy to let it go and have a car that was blatantly illegal, and in the face of a TD that it didn't comply with. We decided that we were not happy with competing with a car that didn't comply with the technical regulations, it's as simple as that.
"Haas is appealing the decision, and we have made a request to be heard as an interested party," he confirmed. "We don't know whether we are going to be allowed to do so, but we are an interested party for obvious reasons, we made the protest. But the rest of it is really between the International Court of Appeal and Haas."