Set file metadata attribute values
I've looked into this question as well, and it appears that the "Data Added" attribute (kMDItemDateAdded) can be queried from mdls (but not xattr), but cannot be set. There is no option for it in the setattrlist function. The comments on this SO question go into a little (but not much) more detail. The "Date Added" value appears to be derived from some other seemingly inaccessible metadata value, not stored as an extended attribute.

I would guess the same applies for the "Last Used" date.