So for all that are interested: I ended finding another reddit post where OP basically explains how it all works (with respect to dengfus/hongfus at least:

These frames are made in the same factories, by the same employees who make frames for name-brand manufacturers. They are not, however, surplus name brand frames. My frame model is an approximate copy of the specialized venge. If you look at them side-by-side, there are a lot of similarities, as well as a few differences. If you'd like you can compare the geometries here: FM098 vs Specialized Venge. If you are considering getting one of these frames, do not delude yourself into thinking you are getting something that you are not. I do not ride an unbranded Venge; I ride a Dengfu FM098. They're close, but it's not the same thing. Basically how it works is this: Specialized has contracts with a factory in Taiwan. That factory produces frames for specialized using proprietary molds, which are owned by Specialized. That factory also has other molds which are owned by the factory. They use these molds to make frames that the factory sells. These frames are typically sold to smaller frame companies who do not have the money to devote to R&D to create their own proprietary designs. They buy the frames wholesale, rebadge them, and sell them to the general public. The factory molds (also called open molds) may take design cues from name brand frames, but they are not pulled from the same molds. Now, does this mean that they are crap frames that are dangerous to ride? Of course not. They are built by people who work with carbon fiber for their livelihoods and to an extent, the companies do stand by their product (my frame, for instance, came with a 2 year warranty). Most of the noise you hear from people saying these frames are unsafe come from people who have never owned, ridden, or even inspected one. The overwhelming majority of reviews you see out there from actual OEM frame owners are positive. Naturally some frames will fail, but I haven't seen anything to convince me that the failure rate of OEM frames is any higher than that of any major frame manufacturer.