Is it an art style change, or are Momo's blush panels, like, super high tech?
Been recently rereading the comic (not the entirely, but a whole lot), and blushing Bubbles/May/Roko are, from what I recall, always depicted as having somewhat animesque, short straight lines on their cheeks. And Roko's chassis is probably towards the high-end in terms of quality.
EDIT: no, sorry. I remember Roko's coworker blushing similarly (her entire face being red), and her face wasn't extremely humanlike. I think that just indicates super-intense blushing that goes beyond the narrow short line. Or maybe there are just two kinds of blush panels, depending on which aesthetic the manufacturer is going for.