A blend is a blend of different fabrics. For example, wool socks and a linen shirt is not a fabric blend, but socks made out of a blend, an interweaving of wool and linen fabric, are. There's not enough information to judge whether it's a moral or practical issue. I would say that if God said not to do it then there's a good reason not to do it. That reason may not be evident, but it's still there.
You wrote:
“There’s not enough information to judge whether it’s a moral or practical issue.”
Incorrect. The law is stated and stated simply enough. You already essentially admitted you understood it to mean blends were wrong to wear. So, if you wear them, are you violating the law (the answer has to be YES) and is that morally permissable (the answer to that logically must be NO). Thus, according to your own logic, to wear blends is morally wrong. Now, do you believe that or do you, according to your own reasoning, deny the law of God?
“I would say that if God said not to do it then there’s a good reason not to do it. That reason may not be evident, but it’s still there.”
So, it is morally allowable for people to wear blends and do you do so?