I have several issues with these statements, and not sure whether to direct them to Mets officials or to Heyman. But here goes.
First, Heilman's best two pitches are his sinking fastball and changeup. However, he also throws a forkball and a slider. That's four pitches by my count.
Second, it's true that Heilman's mechanics are unusual, and they do look similar to the ever-injured Mark Prior's. However, Heilman's throwing motion also compares to those of Don Drysdale, who pitched for 14 seasons in MLB. (Yes, Drysdale did have shoulder issues, but he also threw 270 innings or more 9 times in his career. So was it the motion, or overuse?)
Finally, Heilman may not have a "great" breaking pitch, but he has a decent one -- the aforementioned slider. It's not a John Smoltz slider, but it's certainly more reliable than Mike Pelfrey's.
Which brings me to another point. If the Mets truly think Heilman can't be a starter because he is a "two-pitch pitcher", then I want to know the thought process behind forcing Mike Pelfrey into the starting rotation. Last I checked, Pelfrey is also a "two-pitch pitcher", and his second pitch -- the slider -- is not "great". Pelfrey also does not have an offspeed pitch, while Heilman throws two (changeup and forkball).