I agree that this could be an option for synchronization.
But I strongly disagree this being a default behavior, i.e. not having speed dials folders as it is now. The way it is now is the exact behavior as I would expect and a top implemented feature. I don't want the same speed dials on my work and home PC, and actually need third set for my phone.
I wanted to try the new Firefox Quantum and had a terrible time making it work like this with the Top Sites similar to Opera Speed Dial feature.