Jailbreak to change hardware? No. Just no.
He means will you be able to modify it so that there would be a permanent black bar on the top, and the answer will be yes, fairly easily. There will absolutely be a tweak for this at some point, my guess would be within 3 months of a jailbreak release.
It may mess with full screen apps to a certain degree, ones that use the Ear space as content areas; although I think Apple's guidelines mention to be careful of those areas to begin with, because the content could be cut off by
the notch ™