Hi there,
You are correct, there are no such well angles (90 degree) in the wild, but the breed required moderate angulation both in front and rear for motivation, a slighly longer upper thighs may cause the rear look straight, but doesn't means the angulation is straight. the same as level topline doesn't mean the dog need straight top line......
The modern TRD doesn't developed well angulation as rumous said, the overall modern TRD are only developing more better proportion than the original one....
The problem we have is not about how well the angulation is , it's about how to breed a balance front and rear angulation in a dog, can you get it ?
For your education :
SHOULDER : WELL LAID BACK
Illustration :
The forequarters should be strong and muscular. The shoulder blade must be laid back, forming as closely as possible, a 110 degree angle in its articulation with the upper arm.
THIGHS : WELL DEVELOPED WITH WELL BEND STIFLES
Illustration :
The hindquarters should be strong, broad and muscular. The upper and lower thighs should be well developed with moderate angulation to balance the same degree of the forequarters.