When my husband got his medical and filled out his application, he also was supposed to get a medical for his daughter, even though she is not accompanying. Her medical would be needed in case he wanted to sponsor her sometime down the road. However, since his ex-wife wouldn't allow it, she didn't get it done, and my husband had to sign a statement recognizing that failure to include her medical at the same time as his application meant that he would be unable to sponsor her in the future. If you got the original medical done for non-accompanying children, then maybe that's why they're asking for it again. You'd be unable to sponsor them in the future if you didn't include it. That's just my guess.