WASHINGTON — Southpaw MacKenzie Gore succinctly summed up his advantage on the mound. “I should get left-handers out,” Gore said. “Left-handers don’t like hitting left-handed pitchers.” Gore is improving on using that matchup to his benefit in his first full Major League season. In 16 appearances during his injury-abbreviated rookie campaign in 2022, he held lefty hitters to a .193 batting average, compared to a .263 average by righties. This season, though, lefties had hit .408 against Gore, compared to .201 by right-handers, in his first 11 starts entering Saturday. “We’ve really been surprised, because his stuff is so electric,”…