injurious
First of all, it is absolutely safe, 20W PD fast charge is already a fairly mature technology in the industry, and Apple has also gone through a variety of tests to ensure its security, so in theory there will be no security incidents
Secondly, the battery is a consumable, that is, the use of 5V1A ultra-safe charger will also be lost, the more the number of charging cycles the greater the loss, this is not the tile of the charging head
Using the original charger charging is no problem, long time fast charging will damage the battery