That oft-repeated rumor makes no technical sense to me. It sounds like a typical story started by someone on the internet which hasn't paid much attention to Synpatics's plans.
Synaptics' under glass sensor was NEVER meant to be used under a display. Only under a glass bezel.
Synaptics themselves have said that they'd be more likely to do an optical based sensor when they do in-display technology, since the pixels themselves can act as illumination and sensors.
