I am not familiar with any "offical" rattan rings being taught by any line from Yip Man. By this I mean it doesn't seem to stem from his teachings as a core or even secondary training method. Some people in his line no doubt picked up and perhaps advocate the tool. But it seems to be personal preference. This doesn't imply he NEVER taught it to anyone or that he had an opinion one way or the other. Just. as noted above, it doesn't seem to be a common, or even vaguely used in Yip Man wing chun.
My thought was the reason we don't see it, assuming Yip Man was aware of it, is because it is not fundamental to wing chun. I would make the assumption that if it really developed skills, Yip Man and his students would have advocated its use. Perhaps it is a so called close door thing and all the great masters are hiding in the closet while doing the rings. LOL.
My opinion is there may be some good that can come from the tool. But I think there is equally as much bad, if not more. There are certain moves that dictate the hands be so far apart, but many others that don't. Some people do the chain punch, which I think is partially wrong because it causes a huge circle to have to be performed, depending on how you do the ring. Many other techniques also follow the same pattern and wouldn't be the best approach. Part of the problem is the outward pressure that has to be applied. Granted this isn't always done this way depending on the technique performed with it. I am sure many advocates find wonderful uses for the ring. I am not suggesting it isn't usefully for some, just that it doesn't seem to work for many others. I would prefer to spend my time with another practitioner if available, or work on many other drills and tools like the dummy or pole exercises along with certain other exercises.
Perhaps a good question is, did anyone learn the Ring from Yip Man? Does anyone have the ring as part of their training. Those outside of Yip Man, how do you utilize the ring? Is it a free form drill or more of a set of stuff you practice?
I've only just discovered my error, and I'm going to have to replay whole sections of my life through my mind to see what confusions I may have caused or fallen foul of.
--Douglas Adams