Med Spa Tirzepatide

Starting tirzepatide at a med spa. (not compound)…. why is it that they consider maintenance shots 2 shots a month… rather than 4 smaller dosage once a week! doctors prescribe maintenance as 4 shots not 1 shot every other week totaling 2 shots a month??? I used to spread out my doses and it’s not a big deal but i want to know the reasoning. it’s cheaper for maintenance than 4 doses. ALSO- I asked where they get it from (what pharmacy)and asked them what brand it is and all they did was assure me it’s FDA approved. this is a well known and successful med spa with legit doctors. im just confused on why they would operate like this. does 2 shots as maintenance actually work? and why would they keep the other information confidential? I was on zepbound and they know my history and blood tests.