I've noticed this with my wife too. She loves out children without a doubt, but it's different. It seems to lack genuine closeness and affection.
I was a convert to the religion at age of 20 .... I had started dating a cute non-practicing JW girl in high school, yep, I got sucked in ... But I had a fairly normal, happy, loving family life, so this lack of love that I observed didn't seem right, but believing it's the truth let's you tolerate and excuse the inexcusable.
Being able to cut off a child at the direction of a religion, it's hard to comprehend. I never had to do it, I wondered at times if I would be able to if that time ever came, I'm glad it didn't.
Maybe some JW parents keep the parental relationship somewhat emotionally distant for that reason.