Ok, i think i should be quite a expert on swiss flights
From the usa you get one extra piece. So if you fly economy its 3x23 if you fly business its 3x32
I have flown jfkzrh alot of time with *g and even through they were always 32 kg, they never charged me in economy. So u can try your luck
As a rule any *g will give you a extra piece of luggage by piece concept flights. Its an official agreed on benefit by all * partners
I dont care what the agents told u, They were wrong