Careful with those Chinese studies, they’re not all that rigorous, and are typically there to tout a particular herb or extract. It’s big business in China. Not to say that they’re inaccurate, but there is a definite bias in favor, always.
But, as far as concerns over phytoestrogens, scrolling down to the bottom of your link, there is at least anecdotal evidence of Stevia being used as a contraceptive by women. So, there is some basis, admittedly scant, for the vague recollection.