They certainly had imagination but there's a boatload of difference between a doodle and an actual modern aircraft that happens to have a passing resemblance.

Supposedly the Germans originally swept wings in order to maintain aircraft center of balance and it was only later that they discovered the speed advantaged offered by wings being swept.

Also supposedly the Soviets got the plans on the Focke-Wulf Ta 183 and eventually developed the MiG 15 from them.