It's an overall impression of Chinese martial culture and history formed from a reasonable number of years spent training and studying -- this is not something I can prove by showing a handful of examples in a few minutes, nor can it similarly be refuted. If you'd still like examples, I've given you my own, Chris Parker has given a nice example of Japanese martial arts, and this thread started off with a discussion of Jow Gar of which a brief history can be found
here, which is as good as any for a representative example of openness to cross training.
When you write...
You are claiming that, contrary to most history that I have read, personal experience and awareness of how others train, there is a widespread fetishism for training in one style and only one style. Individual martial artists and clubs may decide not to cross train in a particular art, but that does not generalize to antipathy to cross training as a general principle nor to maintaining an art in a permanently frozen state.
I did not say that it was, my point was that their combination resulted from cross training and thereby cross training made a significant impact on the development of Chinese martial arts. Agreed that the rest is debatable semantics.
True. But words are also actions.
In discussion with others you seem to have changed the question from whether Sanda is Kung Fu...
....to how closely Sanda resembles some 'traditional' Kung Fu arts. Others have made good points e.g. the multiplicity of Sanda. I'll only add with reference to the original question that I think it would be hard to make a case for the majority of ingredients being of non-Chinese origin. Then a case would have to be made that the mixing and baking being done by Chinese in China is insignificant to classification, at which point we may well be removing the 'Brazilian' from Jiu Jitsu and ripping other martial arts from their countries. I guess it's an interesting question.