Even if this wasn't publicly available information, isn't it quite bizarre to act as if you have some better understanding of the difference between F1 cars and sports cars than one of the best F1 drivers in the world? I would bet you quite significant sums of money that he has spent more time driving cars with performance similar to that Mercedes than you have spent driving an F1 car.
We also know that Verstappen races street-legal private cars on tracks during at least some F1 offseasons, something his Red Bull Racing team advisor has shared in interviews with the media.
The idea that some internet posters have a better understanding of the risk profile of taking this car onto a track than one of the best racecar drives in the world is some special HN hubris.