Well, yes... and no!
I'm pretty sure I know the ones you mean and mentioned to the seller that I was certain these were not made by Chance. There have been other cases of lampshades being wrongly attributed to Chance, but after discussing this with the former general manager (1959-81), he confirms the only ones Chance made, were experimental and merely involved modifying large 7-in handkerchief vases with a hole drilled in the centre. Good idea, but Chance never progressed this.
BUT, before everyone sneaks off and starts wrecking perfectly good handkerchief vases, there were only a very few
converted, and probably none that ever survived (apart from one in aforesaid gentleman's garden, which he kindly dug up for me as proof!
So if any of these converted vases do ever appear, I would be extremely sceptical that they were genuinely intended to be lampshades.