You must not be up to speed on how deep fake video works. The mask, which isn’t always used, is put on not to imitate the person but to provide a similar face structure to apply the digital mask over.

Of course it’s a mask like a Halloween mask.

Furthermore, a black undershirt doesn’t make sense as it looks void. In other words, it doesn’t look like black fabric but an empty vector layer. It’s so black that it almost completely rules out a shirt.