I believe this is incorrect - recalculation SHOULD still be done here, because the Attachment DOES already have a permission set on it.

Removing the recalculation in the other method, however, IS appropriate - nothing has actually changed for the PermissibleBase's permissions.

Perhaps a javadoc note is needed -
```java
/**
 * ... this method will perform a permission recalculation, so if multiple permissions are needed
 * on the attachment, {@link #addAttachment(Plugin plugin)} is better to use.
 */
```