Why do you think there would not be a P version of M3? We know Tesla wants/needs to sell as many high priced M3s as possible to maximize revenue while the ramp proceeds more slowly than anyone expected. That's why they began with the LR M3 first.
Just because a P isn't shown yet on the website M3 design studio means nothing.
I spoke with a Tesla sales rep connected with M3 reservations and ordering last week. I selected to go on hold because I want at least dual motor. I told him I also wanted to see what price and performance would be for the M3 P75D before I ordered a dual motor. He said that made sense and others were doing the same. He said nothing to suggest a P won't become available sometime later this year or early next.