It's unfortunate to see Gladden attempting to advance this stereotype of the Twins' hitting approach.A hitter that is looking to pull the ball all the time is going to get taken advantage of by MLB pitchers.It might work in the minors, but it's rarely sustainable in MLB.
Ortiz, Gomez, and Hardy are commonly cited as guys the Twins tried to break by teaching them how to hit the other way when situationally appropriate.The irony there is that when you look at their splits, Ortiz and Gomez had really good seasons after leaving the Twins by doing something... I'll let you decipher it yourself:
Ortiz, 2002 with Twins.wRC+ by field: 259 to RF (pull), 66 to CF, 74 to LF
Ortiz, 2003 with Red Sox (breakout year).wRC+ by field: 205 to RF (pull), 152 to CF, 149 to LF
Gomez, 2008 with Twins.wRC+ by field: 183 to LF (pull), 45 to CF, 91 to RF
Gomez, 2013 with Brewers (breakout year).wRC+ by field: 261 to LF (pull), 150 to CF, 154 to RF
For those unfamiliar with wRC+, it is a number weighted to league and park factors with 100 representing
league average offensive production.
Hardy is the exception and has stayed a 'true-pull' hitter.This has given him 20 some homers most years which sounds great, but his overall offensive performances have varied above and below league average.
While that's true about Ortiz continuing to use all fields, you have to remember how this works in action. It isn't that the Twins didn't let him pull the ball, it's that they asked him to back down on trying to hard to pull with authority.
Where you see the spike for Ortiz from 2003 on isn't in how his spray chart looks...it's in how he went from being mostly a line drive hitter with some flyballs to being a balanced flyball/line drive guy. That's where the power surge came from - he was not only turning on balls but he was allowed to unload on them as well. When you're worried about plate coverage and going the opposite way, I can see how that would limit the authority you swing with on inside pitches.