Who cares about the NY Mets complex being so great. I wouldn't want my players relaxing, playing on the computer, living in a hotel style dorm. I want them to stay focused on baseball and nothing but baseball. For these kid to succeed in getting to America, they don't need any distractions.
At the same time... I'd imagine it creates a higher amount of flame outs once they hit state side because they'll finally have free time.
Maybe the Mets want to see how the kids deal with distractions before they make the big jump of bringing them state side.
Don't think either approach is wrong, just two schools of thought.