Oh, Susan. You and the wacky things you’d say out loud in an out of character fashion before I knew you’re character better. Or maybe that was influenced by her fusion with Jeremy? Jeremy would not be shy about saying, well, pretty much anything.
Panel two is definitely a bit of lampshading (as in drawing direct attention to something that one may find questionable in a story), though it still wouldn’t explain why Tedd didn’t let William and Gillian use them. I mean, yeah, he’d have to ask his dad’s permission, but why would he say no? He’d probably make an extra effort to make sure they were readily available for that.
So yeah. Sorta explained, but not really.
I don’t 100% recall why I thought the watches were necessary in a world with cell phones (as Amanda herself asks), but maybe I’ll recall later.