There are a few other threads about the inability of the posters and crapload of others that replied to hit high fast-balls. I agree it's like a spam. I've actually put the pci at the top of the zone and started my swing at various times to test it, and it truly is not allowed by the AI.
When AI is in shut-down mode it just dictates all fast balls over 98 mph to be impossible put put into play. Many other unusual things in AI shut-down mode, but it is very consistent with no fastballs put in play. And also the prolific "swung-through it" for most many other pitches.
Some have said this is possible with a monitor as opposed to TV? Why would a gaming company ever condition their software based on display? Doesn't sound logical, but anything is possible I suppose.