You are right that in a few cases, the CPC distinguishes between products that are set up for retail sale and those who are not. This is typically due to differences in the way the product is measured, packaged and presented to the customer. When such a distinction is made, you would expect to find a similar class nearby where products intended for wholesale would fit.
Since the goods part of the CPC is built on the Harmonized System (HS) classification, maintained by the World Customs Organization (WCO), the same definitions that the HS uses in this case have been carried over to the CPC. I have added the relevant HS explanatory note for retail sale of yarn as an attachment.
Attachment
In one of the subclasses you mentioned, there is an error in the CPC text, which will be corrected. This is CPC subclass 26330, where the correct text should read: "Yarn of wool, containing less than 85% by weight of wool, not put up for retail sale."