I could be wrong but I’m guessing you are Referring to a MSF BRC (Basic Rider Course) and ERC (Experienced Rider Course) There is an Advanced Rider Course-ARC but it is not as common and less than 2 years old.
I think you will see some of this change in MSF in the future. Some instructors are adamant that four fingers have to be used. However, I have never found it in the curriculum that is it “required”. I’ve had some conversations with MSF Rider Coaches and a few Rider Coach trainers about it. MSF classes are at a level so that students with no previous experience can ride a bike. The methods taught will work on any motorcycle. I have converted a few to my thinking on the subject.
In my opinion it depends on the rider, their skill level, and the strength of their hands, the bike they are riding. As long as the students are able to achieve maximum braking power with two fingers I don’t say anything at all to them. More often the opposite is true, however. The average student who is attempting to stop with two fingers on the front brake is not stopping in minimum distances. It is also fairly rare for a person to show up on modern sport bike. 90% of the bikes I see in class are our own trainers, or student owner cruisers. While I can still apply maximum braking power on most of these using two fingers, experience starts coming into play. Most of the time when the student starts using four fingers, I start seeing smoother applications of the front brake. I also see more compression to the front forks and in a progressive behavior. Stopping distances start to drop dramatically. Again however, if I’m already seeing decent results with two fingers, I’ll work with them in that method. But I’ll never encourage them to make a transition from 4 to 2 in a BRC or ERC.
The ARC recognizes more advanced techniques and even mentions two finger braking of sport bikes in the materials related. I have not taught it but have seen some of the program, and the Military specific one. I’ve have also been certified in the Military AMC Sport Bike training program. I don’t think you’ll ever see all of the “high performance” techniques taught in any MSF course. There are just too many for the amount of time and the students they target.
If you can achieve maximum braking with two fingers, go for it!