On Earth-1, we may see Tom Cavanagh’s face when we look at H.R., but the public sees him with a face constructed by a light refraction device.
The tech has allowed H.R. to continue to be played by Tom Cavanagh without requiring fans to suspend all belief about Central City folks not recognizing him.
As longtime Flash fans will remember, Harrison Wells is known as a villain on Earth-1 due to his actions in the earlier days of the series.
In fact, the show had to invent a special kind of Earth-19 technology to explain why H.R. could wander around Earth-1 without anybody noticing.