It's not angle but radius - you can go round in loops if you keep the radius large enough. What that radius is specifically depends on all several things, manufacturing, materials and signals (type). The point being if you bend any high speed cable too tightly it will be prone to failure. That doesn't necessarily mean it will instantly fail but rather be more likely to drop out or transfer more slowly or indeed fail entirely. Even larger than the minimum can still fail because of movement. eg plugging it in and out causes movement. We're talking high frequency stuff here (GHz), sometimes very high, and that stuff is black magic even to those that design it
Or to put it another way, cheap Chinese cables are fine if you don't "operate" them out of spec - granted their spec will be worse than a good quality one.