I've been taking my E sublingualy since the very beginning, and have had no problems whatsoever. Feminization has been pretty much ongoing, and I definitely can't complain about my results. 1 year in, and I'm already now living in a body that looks more female than male in terms of overall shape, skin texture, and body hair.
I've actually heard the opposite of what you've said... that doing it sublingualy is actually better for feminization. Because when estradiol has to pass through the digestive system, a lot of it is converted to less-potent derivatives like estrone and estriol. (Estrone is 10X less active than estradiol, estriol is 80X less active.) Where when it goes directly into the bloodstream, most of it remains 17β-estradiol, the most active form of estrogen. Plus it lessens the risks of clotting and liver damage.
Me personally, I've never seen a single study claiming any benefits to oral. Every single thing I've read points to sublingual being superior. And again, it's worked for me, so I can't complain.