I don’t think that’s true. I think you could stay on reserve at ORD until you get a line at LGA. Unless you get a line where they tell you and have to commute until he can get LGA?
I’m new and trying to do the same thing. I live in SAN, will ask for my domicile/line there at first opportunity, but then commute if I get a line in ORD or LGA or wherever until I can get transferred to SAN. I might rather stand reserve in SAN before I got a line, but it sounds like you commute to a line they assign you if needed, instead of just standing reserve where you want. Reserve at home sounds like maybe an extra thing you can volunteer for as well as picking up trips where you live. Do I have that right?