It's normal. Girls can be pretty intimidating to boys in those middle years.They tend to mature earlier. The 10-year-old boy can still be very much a "little kid" while the 10-year-old girl can be developing and taking interest in "relationship" behavior and chatter. Boys can feel pressured to move into this world before they are ready and and under the microscope in everything they do or say around girls. I know my own son was frustrated in the behavior change of his female friends starting about that age. Suddenly they were always asking "who do you like" and teasing him. He'd wear a new shirt and they'd all comment and make him feel self-conscience. It was unwanted attention that he was not developmentally ready for. At 10, he'd get downright angry at them. At 13, he rolls his eyes and ignores the obnoxious ones but manages to have some female friends that are "OK" in a groups setting. In a couple years, he'll likely be comfortable again.
I agree with your husband. It'll pass.
Married mom, DD 18, DS 15, and a Valentine's surprise on the way!