I was taught (both in Europe and US) to slam the flaps up after T/D to reduce landing distance. Then we had a solo student accidently raising gear instead of flaps during roll-out, combined with back pressure on the yoke the squat switch did not prevent the gear from coming up
Did the school learn a lesson? I don't know, they introduced a new challenge "confirm flaps" from student, to be responded "affirm" from instructor before allowed to raise the flaps. All this still taking place during landing roll-out... Do I like the whole thing with raising flaps, NO! Does it make a difference? IMO, Yes... especielly on the BE76 its very easy to lock the wheels if braking too hard. If you get the flaps up, you can stamp them through the floor and braking is very efficient. On the other hand, I don't know any normal airfield where it would ever be necessary to do so. If you are just on speed, on spot you should be able to stop with plenty of room.
What I really don't like is that some students develope a habit of always raising the flaps during rollout after ANY landing. Training is just as much about habits as it is about skill, so if it wasn't for our SOP I wouldn't teach raising the flaps while still at high speed during landing phase.