The clincher is MSU is talking about trout that are not artifically fed and must subsist on natural feed. In that case yes there is competition with minnows vs. trout. However as Ed says the larger trout can and do feed on fish -- especially fatheads which are too slow to escape. From research I have seen the major switch off from insects, zooplankton etc. in wild trout is about 16 inches. Of course it depends on if minnnows are available. Also brown trout are more carnivorous than the other species. I do fish one lake for planted rainbows where nitecrawlers out fish minnows 10:1 even though these trout run from 15 to 24 inches.
I also believe the length of time a trout has been on pellets has some bearing on how quickly they will take a minnow. My trout are so conditioned on pellets they will ignore a floating insect, and even have been known to ignore minnows and nitecrawlers. The browns I plant my pond with are already 2 to 3 years old so they've been on pellets for a while.
FME (From my experience) if you want big trout, and more trout per acre, feed them pellets as it's more cost effective anyway.