I assume that no other bullpen has zero lefties in it.
The Astros went through much of 2019 without a leftie in the pen. Both Ryan Pressley and Will Harris were better against LHBs than against RHBs. They also didn't have a LHP in the pen in their run to the WS last year.
L/R doesn't matter if RHP's can get LHBs out.
https://blogs.fangraphs.com/the-astros-dont-need-lefties/
