Many businesses can be registered with Tong Ren Tang name. Just pay some license fee, maybe. Say if you want to open a business, you can have the Tong Ren Tang name too. You are just the reseller. You can resell any medicine, including ever health food or fake medicine. So Tong Ren Tang is not really Tong Ren Tang, it is just a reseller. No credits. You can see many Tong Ren Tang has all kinds of medicines from varies vendors.
So don't trust Tong Ren Tang names so much. But you can trust Tong Ren Tang medicines really made by TOng RenTang. i.e. trust the vendor, not the seller.
i don't think they sell fake products. i guess you have to bargain for lower prices when buying, otherwise they just treat you like tourists and sell at much higher prices.
I am canadian and I went to Beijing in March. I was cheated by the travel company and the Tong Ren Tong. They told me it was the Central one (not branchs) but I checked the web and they made it up. It was just a branch (reseller).
The medicines are fake after I check the web. They are just healthy food from other company instead of Tong Ren Tonga.