For what I know that effect is negligible. Here's a review of some studies on the topic:

https://nutritionfacts.org/video/who-shouldnt-eat-soy/

See my other comment on T-level being higher in vegans (Even higher then in vegetarians). There's a huge vegan-fitness movement going on, and it rapidly moving into professional sport in general. They simply self-report to perform better, thus stick to the diet.