All I have to say is: be careful!
Very low percentage of MtF's have this capability to shriek super high up there after 1st pubertal voice change, and if you try to force it without gradually training yourself back up there (if even possible) you can easily do irreversible damage to your vocal cords.
I lost my ability to shriek when my voice changed as a teenager, and even with vocal fold shortening I am still unable to do get back up there... Although I am able to squeal now

After VFS I can shout much higher than I used to be able to (and it does sound very feminine), but I never push it too hard because it is plain dangerous. You could easily land yourself with a hemorrhage and a disabled vocal fold which to put it frankly screws a lot of things up.
Everyone please promise to be very careful when testing their limits!