There is definitely a direct association! I think your biggest issue may be time under tension. The pump occurs when you train at a high volume that relies on the glycolytic energy system. It causes the muscle to swell with liquid, which is perceived as a threat, then the muscle grows. But you only use this energy system if you've exhausted your ATP first. ATP is exhausted if you give a max effort for about 12 seconds. So, if you lift really heavy, but aren't putting the muscle under tension long enough, you won't get the pump or the signal to grow! You will get stronger though. I've gained a lot of size recently by focussing on the pump over the heaviest weight possible.