You might be interested with the results of this experiment at:
http://www.ctmuzzleloaders.com/mlexp...corrosion.html
Now they didn't test Bore Butter but they did test Wonder Lube and I have read that Ox Yoke supplies TC with Bore Butter and it is only a minor variation of Wonder Lube. From my own observations, they sure seem to be almost the same so I would say that you could expect the same results from Bore Butter.
From the results of this test you can see that Wonder Lube didn't do too good of a job at corrosion protection. It is not that the Wonder Lube caused the corrosion but did not adequately provide protection from it. This is probably what the person that responded to you meant.
Now notice that in this test, burnt powder residue was purposely left on the metal test strips and they were not clean. If they were clean, there may very well not be any corrosion problems, at least not in the time periods between using the rifles and recleaning. However, I think it would be fair to say that a product that offered the most corrosion protection, even with burnt powder residue present, would be better for storage of a clean rifle.
FWIW, I do use Lehigh Valley Lube for shooting and do think it is an excellent product, both as a patch lube and for cleaning. I don't normally use it for a thorough rifle cleaning, but have used it when I am away from home and just need to clean and store the rifle for overnight. I also do not use it for corrosion protection of my stored rifles.