That's been reported anecdotal,y, but no studies have been done to show it to be true. It may be, but I doubt it in this case. The reason given in the other cases has been the bacteri contamination, as the cloth they were testing was severely contaminated with mold and lichens and bacteri from years of exposure. The Shroud is remarkably clean of such contaminants. We DO know what happened in the 1988 C-14 test. . , three different, mutually exclusive approaches have prove that what was tested was a patch made of cotton, probably made in the sixteenth or seventeenth century to repair that frayed corner. We still have the fifth unburnt sub-sample that was retained from the 1988 test and one half of it is Cotton, one half Original linen. Documentary evidence has been found backing that.
Carbon dating of textiles has had problems with accuracy: an Egyptian mummy-wrapping (Manchester mummy collection) showed an age 700 years younger than the body.