@ The prof - while I have no evidence as to what extent this is true, I believe that to some large degree, you are confusing cause and effect.
Which seems more reasonable to you on the face of it.
"Due to taking a step that usually increases sales, sales decreased"
or
"Due to expectations that sales would decrease, developers took steps that would normally increase sales".
For instance, FF13 was a bad game, it was a bad game before the 360 version came out. The devs released it on 2 consoles to sell more. There reason it sold poorly was because it was bad, not because it was multiplat.