Noticed how the rear seating is higher than the front one for better visibility. So this is actually an improvement compared to the F-16B and other US designs like F-14 & F-18B. Russians have been following the similar approach for their twin seaters as well.
Not necessarily an improvement. To date, there is no hard data to support the argument that a trainer version of operational aircraft that have raised rear cockpit seat is better than one without. You would have to look at highly specialized platforms like the SR-71 to see such a structural change is justified. Hard data in terms of safety, higher student performance, or faster certifications. All has to be directly attributed to the higher seat position from the rear cockpit. Good luck on that.
I am willing to speculate that the B version with the higher rear cockpit seat is purely because of internal structures. A frontline fighter is not a trainer. If a frontline fighter has a trainer version, it is for familiarization and certification, not to train a student pilot on the principles of flying. By the time a pilot is assigned to the unit, either he is a graduate of the air force's flight training or he transitioned from another aircraft. The MIG-25 trainer version has no radar and no combat capabilities and it is likely that the jet's internal structures were not amenable for a two-seater arrangement unless other systems had to be sacrificed.
Internally speaking, right behind the cockpit is a fuel tank. To make a trainer version of a frontline fighter, removal or reduction in size of this structure is necessary. Below the cockpit could be nose landing gear bay, weapons bay, or avionics bay. These structures are not as easily modified as a fuel compartment. So installing a second cockpit usually end up with the second seat being slightly higher. There is nothing extraordinary about it.
By the time a new pilot is assigned to the unit, he already earned his wings. He passed all the physical rigors of flight and did not vomit in training. He was trained in flight related issues such as fuel management, communication, take off and landing, or formation flying. In the trainer version of a frontline fighter, he would be trained on the unique systems of the jet and his instructor in the rear cockpit would be guiding him on those unique features.
On the few early familiarization flights, the new pilot would be in the rear cockpit. Something like transition from a jet that has a center stick to one that has a sidestick. That would need a few flights in the rear cockpit. Then once the new pilot is fully acclimatized to flying with a sidestick, the student and IP would trade cockpits.
