Despite year after year of delays, it seems that the in-display fingerprint scanner, alternatively called a fingerprint on display (FOD), is still a goal among smartphone makers. Some are just taking a different route. Vivo, for example, used Synaptics' optical fingerprint scanner on its X20 Play UD, the first commercial phone to sport that feature. But being under the phone's screen and, therefore, subject to the same wear and tear as the display might raise some doubts and concerns over its reliability. To answer those questions, YouTube Marques Brownlee, a.k.a. MKBHD, puts that FOD to the test.