The 1g of protein per pound of weight is pretty much strictly for weightlifting, because building the muscle mass (vegetarian or not) simply requires it to hit the 2-3 times weight major lifts. Anyone telling you to do it otherwise ain’t no health professional.
And even then, it’s 1g per pound of your healthy weight range, so for a normal man it’s still a relatively normal amount of protein; like if 180 lbs is a healthy weight, that’s basically a normal American diet’s level of protein. My family doesn’t eat a lot of meat so now that I’m back to training I use whey, but I am giant and should have around 200-220g of protein when weight training. Calories matter so much more, and the healthy calories even more.
And this is coming from someone who briefly went on testosterone supplementation because of a petuitary distinction and always has low testosterone - and who never really had issues weightlifting once I was able to peel away the “pay to fail” industry crap. I never believed low testosterone contributes as much as advertised to fitness results or overall health.