The phrase vascular occlusion refers to restriction of bloodflow. This is sometimes done to create hypertrophy adaptations in bodybuildings. See for example the Wikipedia article on training or these T-Nation pieces:
- Sep 2013 https://www.t-nation.com/training/blood-flow-restriction-training
- Jun 2016 https://www.t-nation.com/training/tip-try-blood-flow-restriction-training
- Feb 2017 https://www.t-nation.com/training/tip-build-quads-with-occlusion-and-tension
- May 2017 https://www.t-nation.com/training/tip-occlusion-training-for-big-calves
It is unknown whether or not the smooth muscle of the penis can hypertrophy in response to this, but if so, the occlusion created by fucking tight pussy instead of loose pussy may induce penis growth.
Given there is lying propaganda saying that the dick "does not contain any muscles" this likely means the smooth muscles are very important and people are trying to obstruct knowledge of that.
It should be noted though that erections are caused by the RELAXATION of smooth muscle tissue. It is their passive tension which keeps blood out of the penis.
If there is any possibility of adaptation it would be due to sarcoplasmic (not myofibrilar) hypertrophy.