Yes, when I have gone through screening points with a toddler, the agents (multiple airports - IAH, DFW, CRP) ask if she can stand still for the NoS. I say no, and they wave me through the WTMD, even when no one else was being allowed to go through it.

When they have been directing people to alternate between NoS and WTMD, I don't make eye contact to get my instructions - I just head to the WTMD with the child in my arms. It's something akin to the concept "It's easier to ask for forgiveness than permission". Don't show weakness (or antagonism). Just look like you know exactly what you are doing - going through the WTMD.