I assume the brake light switch in the '07 is the same as in my '04.5...
When you press on the pedal, there is a little slop in the eyelet from the hydroboost. Just before the brake pedal pin presses on the rod, it hits the brake switch. If there's not enough slop, the pin engages the rod from the hydroboost without engaging the brake light switch.
When replacing a hydroboost, it is sometimes necessary to hog out the eyelet so there's enough slop. (Others have shimmed the switch, but I think ensuring enough slop is the way GM intended it to work.)
It's something to check.
2004.5 Silverado 3500 SRW 4x4, D/A (LLY), Ext. Cab, Long Bed
engineer837 aux rad, TxC CAI, LBZ MP, Scangauge II, Nicktane aux filter head, KD lift pump, 2008 PS pump, 2011 hydroboost, Frederico Swaybars, Rancho 9000XL, Torklift StableLoads, BFG AT/KO2, Lance 835 Camper often in the bed.