I think they're also betting on 16 year olds, they have signed Pujols, Encarnacion and Ortiz the last few years, but infielders tend to be fast with good hands and catchers have strong arms, so you can move them around as they mature.
This may also reflect that most American prospects tend to end up as OFs, and good infielders and catchers are at a premium at the major league level (look at the leaders among 2B, SS, C and 3B and realize that if you can develop one with plus fielding and .750 OPS you have great trade bait).
Plus, because LA players are 16, you have an interesting gamble, the best LA players will be the ones with early growth spurts, but they're also likely to flatline (which may explain why there are so many busts), while if you focus on good athletes with speed and eye to hand coordination who haven't experienced a major growth spurt, you might get lucky.
I'd point out that this is just the Venezuelan haul, where their advantage on the ground makes it logical to invest, I presume they also have scouts in the DR, Panama, etc. So more signings may be on the horizon.
Note the emphasis on the "hitting skill," with 16 year olds, the power may come later, so the hitting skill probably reflects quick twitch reflexes and eye to hand coordination.