I mostly call my moms by their first names. I almost never directly refer to them as "mom." When talking about them to people who know them, I refer to them by their names. Basically only call them my mom to people who don't know my parents.
I'm in the US. But I think part of the reason I do that is having multiple moms. OTOH, they are trying to teach our niece to call them grammy and nana and I know my cousins have a similar way of differentiating their moms.
Given how long they've used windows XP for their computers, doesn't surprise me.