It seems deceptive to me to claim one percentage but knowingly have another. I can see where it might be a difficult thing with nutrients, but it is fairly straightforward with woven items. From the Cashmere and Camel Hair Manufacturers Institute; this is a US POV:
Mislabeling of luxury fibers in woven and knit garments is a growing problem for U.S. retailers. Many imported fabric suppliers and garment manufacturers misrepresent fiber content in order to unfairly trade on the image of luxury fibers, such as cashmere and camel hair. It is important that retailers are alert to this problem, because both federal and state laws hold retailers responsible for the accuracy of the label information on the garments they sell.
And the 3% variance is for wool, not cashmere:
https://www.ftc.gov/tips-advice/bus...cashmere-complying-wool-products-labeling-act
Fiber Content Disclosure
Product labels must reflect the true fiber content of the item. For example, if a sweater is made of wool, it can be labeled as 100% Wool, assuming it contains only wool. Likewise, if a sweater is made only of cashmere as defined in the Wool Act, it can be labeled as 100% either 100% Wool or 100% Cashmere. If a sweater contains cashmere mixed with sheeps wool and the label refers to cashmere, the label must accurately disclose the content, for example, 80% Wool, 20% Cashmere. It would be illegal to say simply Cashmere or Cashmere blend without stating the percentages. One exception to the requirement that percentages be stated: the word All can be used in place of 100% if the product is made of only one fiber; for example, All Wool or All Cashmere.
If a claim about the fiber content appears elsewhere on the garment, say a sleeve label, it must mirror the garment's fiber content label. For example, a coat labeled 50% Cashmere, 50% Wool cannot have a sleeve label stating only FINE CASHMERE GARMENT or FINE CASHMERE BLEND. In this instance, the sleeve label also must say 50% Cashmere, 50% Wool in equally conspicuous lettering.
The amended Wool Rules allow hang-tags that identify fibers including cashmere, but that dont disclose the items full fiber content if:
the item has a label that includes the required fiber content statement, and
the hang-tag tells consumers to see the label for the full fiber content, or states that it doesnt disclose the products full fiber content.
These disclosures aren't required if the garment contains only one fiber and the hang-tag identifies that fiber.
The Textile Act allows a 3% tolerance for fiber content claims, but the Wool Products Labeling Act doesn't. However, the Wool Act says that deviation from the stated fiber content is not considered mislabeling if it results from "unavoidable variations" in the manufacturing process that occur despite the exercise of due care. For this reason, the FTC generally applies the 3% tolerance to wool products. The 3% tolerance does not allow for intentional mislabeling. There is no tolerance for a 100% claim, because the addition of another fiber would be intentional.
In other words, yes, it is possible a variance will be tolerated but manufacturers must aim for accuracy. They can't say 70% knowing it's less. That is fraud.