The charging hot you say should refer to the earphone when the charging bin is charged in the charging bin, because: the heat transmitted by the charging bin, then the heat is normal, and the earphone itself has no impact, because it is a simple energy loss, and the earphone is composed of hard plastic, which has relatively high requirements for heat resistance and heat resistance.
According to my understanding, the AirPods 2 charging case will generate slight heat during charging, which is a normal phenomenon. However, if the charging case overheats or feels unusually hot, it may require attention and further examination. It is recommended that in case of doubt or uncertainty, you can contact Apple's official customer service for help.
A little hot while charging is normal.