PEDs seriously tainted their records. I hate to defend their achievements, but even with PEDs you still have to hit the ball. I don't know that PEDs improve the necessary eye/hand coordination needed to hit the ball.
PEDs impact performance by allowing players to train longer and harder without their muscles fatiguing, resulting in fewer injuries, thereby extending the careers of older players. The ability to train longer and harder dramatically improves strength, particularly related to fast twitch muscle fibers. This allows hitters to be “quicker” with their bats and pitchers to throw harder and longer.
Add in the use of amphetamines, which some hitters took to improve their concentration at the plate and you end up with a hitter who is stronger, intensely focused with a really quick bat. So while PED’s and amphetamines do not improve eye/hand coordination, they permit a hitter to use whatever eye/hand coordination they posess to tremendous effect.
Bonds, McGuire & Sosa were all very good hitters when they got to the majors, with the ability to hit HR’s. What was unique was that when performance starts to decline for most players, each of them got much bigger, adding significant muscle mass in their 30’s, hitting improbable HR totals that they never reached in their primes.