Side-ring EXTRA · Kapparah limited to tumas Mikdash
Rashi (Toras Kohanim / Shevuos) limits the atonement effected by the Kohen Gadol’s bull: it covers only the Kohanim’s offences of tumas Mikdash and Kodashav, not other sins.
English: All of their atonement is solely for the defilement of the Sanctuary and its holy things, as it is said “and he shall atone for the Holy from the impurities.”
Limited scope of the bull’s kapparah
The second vidui and the subsequent slaughter of the bull cleanse the Kohanim only of sanctuary-related impurity offences. Other sins require other mechanisms of kapparah.