According to Material Design Typography, the font sizes for body 1, body 2, and Subhead styles are different for desktop vs device media.
Currently, the styles are set to desktop styles and not device styles. The font sizes should update upon device change.

Need to check with Material UX for what they consider to be "device" vs. "desktop" for typography.
@joeyperson Do you have any info on this?
Lowing the priority on this since people can easily to their own media queries to tweak the font size.
any update on this issue? Ux team? I need to use it and I have to decide what to do.
Issues like this make me think it was a mistake to incorporate the entire MD layout system in my markup. Better off just sticking to CSS.
This issue is closed as part of our 鈥楽urge Focus on Material 2' efforts.
For details, see our forum posting @ http://bit.ly/1UhZyWs.
Most helpful comment
Issues like this make me think it was a mistake to incorporate the entire MD layout system in my markup. Better off just sticking to CSS.