Like so much of other teachings from the WTS that they are wrong on, they are wrong on this as well.
The prophesy of saying peace and security and the destruction that occurs thereafter does not occur kicking off the GT, it occurs kicking off Armageddon.
The saying peace and security is tied to Rev 11:10 which occurs AFTER the 42 months (GT)...
[Rev 11:10 And those dwelling on the earth rejoice over them and enjoy themselves, and they will send gifts to one another, because these two prophets tormented those dwelling on the earth.]