I'd still say there are more Christians that know the Christian faith better than atheists and agnostics, but percentage wise it probably goes to the latter.
But in terms of knowing about religion as a broad term, I'd definitely agree. I went to a Baptist church growing up that wasn't progressive but it wasn't your typical conservative Baptist church either. My youth pastor took 2 months taking us to different churches of other denominations and holy places of other religions. We came back to our church and discussed the differences, but never once did anybody teaching us say how they were wrong. I remember some parents being upset, I think one family left the church if I remember right, but most thought it was a fantastic idea. It's important to know how your faith differs from others, but most churches just take an us vs. them approach.