Rems not scaling as expected

I was happy to see rems as an option for text. (I like to design for usability for all). The rems scale weirdly. With the same rem size at all 3 breakpoints I expect the text size to stay consistent. For some reason at tablet breakpoint the text size shrinks. Will it actually be fine on the live product? Or is this a bug? (I see some other unexpected scale issues too.)

here is my example.

New users can only add 1 screenshots. So I am adding the others as comments.