the coding is undoubtedly taking the last change date and user from the SY structure:
IF neuflag = space
and ( not rmmg2-new_inst is initial or
not rmmg2-new_inst_v is initial or
not rmmg2-new_inst_a is initial ).
mara-laeda = sy-datum.
IF user IS INITIAL.
mara-aenam = sy-uname.
ELSE.
mara-aenam = user.
ENDIF.
ENDIF.
And this sounds logical to me, as if this would not be the case, then you could change data with an IDOC and let it look as if this change was done by someone else.