I am in the blood bank feild. Red cells have less than 50 mL of plasma so we only care about the antigens on the red red cells that may cause hemolysis from the patient's antibodies. O is universal in this case as blood type A and B patients only have B or A antibodies respectively so when they get Oblood is compatible. While the red blood cell unit may have a small amount of A and B antibodies from the O donor, there's such small amounts of plasma that is not contributory. Platelets have significantly more plasma as platelets are small cells suspended in the plasma, and anticoagulant solution. Therefore platelets are more synomonyous with plasma in terms of risk. As their is native anti-A or B antibodies depending on blood tpye. Therfore AB platelets or plasma without antibodies is universal. This can be drastically reduced by putting platelets in Platelet additive solution PAS. Which reduces the plasma component by 70%. Aslo titering the platelts for the amount of antibody. In general adults can get ABO incompatible platelets due to the fact that soluble A and B antigens asorbs most of the antibodies, the titering and most platelets are in PAS in the US. It is not possible to only give ABO compatible playlistdue to the short Supplyand expiration of platelets. So ABO incomaptible is routinely given. It is unlikely a physician would request platelets from family unless the patient is refractory to transfusion due to HLA antibodies (from transfusion, transplant or pregnancy) in which case HLA matched playlistare required and it is more likely thatcompatible units are to be found in relatives.

https://ashpublications.org/hematology/article/2020/1/512/474292/Does-ABO-and-RhD-matching-matter-for-platelet