Soylent is an actual meal replacement. You can consume nothing but Soylent for as long as you want to. It's not geared towards weight loss, just as an alternative to food. It provides complete nutrition.
Also I can't find anything on the site today, nor can I remember any advertising in the past that would lead me to believe it's a gendered product. SlimFast aggressively advertises towards women, sure, but I fail to see how Soylent is geared towards men.
Soylent took this concept, took the NG/PEG tubes out of the equation and sold it to those who are alive and well.
They have have taken what is possibly one of the least attractive products imaginable -- a product that is expensive, tastes awful and initially afflicts many people with diarrhea... and successfully marketed it.
For most people what looks to be a diarrhea in reality is a mildly violent reaction to the changes of your feeding habits and thus the changes in your metabolism. In rarer cases, I've known people consuming Herbalife who, even though they admit they feel MUCH better, occasionally puke -- that's the rarer form of the body flushing itself.
So this seeming diarrhea is very normal in the first phases of weight loss -- or even simply starting eating healthier and ingesting more water without aiming for a weight loss.