letter stating losing sdp six months in advance

hi me again.hope im writing in the correct place .im currently in support group esa n back in february i received a letter stating i will receive less money from august 2023(cant remember the exact date) it just seems strange that im having my pip review next week..has the decision already been made then even though i havnt yet had my assessment yet? or is it a standard letter they send out? i never used to get the sbp part until my last pip assessment .thanks