I've been to many spring training games at Hammond, and I would put no stock into that reading. Last time I was there, they had Duensing registering at 96.
Having said that, the pitch was probably somewhere in that neighborhood, and that's a good sign. Gibson should be quite nasty if he's sitting in the mid-90s.
I read several reports that talked about the Hammond Stadium gun, that also mentioned that a scout had him top out at 95. Have also read in several places that Gibson will not be in the bullpen, in Minnesota, Rochester, or elsewhere. The reasoning given was that he has never been a reliever in his life. I don't have a clue whether he will begin his career with the Twins or somehow limiting innings in either Rochester or EST. It seems to make a lot of sense, however, if he is going to be limited and miss a month, it makes a lot more sense that it be April rather than September...thus, adding another year to his team control.