Those Chinese chemical companies and drug suppliers are not transacting on SR. They are clearnet businesses, sometimes with clearnet web sites, and always with clearnet email addresses. They take fiat currency, not bitcoins. They probably don't know that the people they are selling to are SR vendors or buyers. That is what makes unencrypted emails to these sources on the Tormail server such a big vulnerability, if it was indeed seized by LE. Sources up the supply chain will be compromised, as well as potentially the vendors who provided shipping addresses in plaintext that can be linked to them.