Roman has an .800 OPS vs LHP, which is well above league average. It is a limited sample size, however.
The difference between LHH vs LHP and RHH vs RHP is probably not as great as you think. Over the last 3 years, LHH have anout a .675 OPS vs LHP, while RHH have about a .700 OPS vs RHP.
Of course that’s really not relevant, since we’re talking about two very specific LHH’s, one of who is Roman Anthony, whose numbers vs LHP are unlikely to drop just because Wilyer Abreu struggles vs LHP.
Not to mention, not every team has an endless supply of LHP in their bullpen, and teams rarely carry LOOGY specialists now, as they were obsoleted by the 3 batter rule…