mod_assign_save_grades Notifications

I'm using mod_assign_save_grades API for updating students grades, and every time the grades change the students get a email notification. I am unable to turn off this notification.

I tried turning on and off the Notify Student checkbox and all the notification options in the assignment settings.

Is there maybe a API argument to turn it off, which I am missing?

mod_assign_save_grades

General structure

list of ( 
object {
userid int   //The student id to operate on
grade double   //The new grade for this user. Ignored if advanced grading used
attemptnumber int   //The attempt number (-1 means latest attempt)
addattempt int   //Allow another attempt if manual attempt reopen method
workflowstate string   //The next marking workflow state
plugindataDefault to "Array
(
)
"//plugin data
object {
assignfeedbackcomments_editorOptional//Editor structure
object {
text string   //The text for this feedback.
format int   //The format for this feedback
} 
files_filemanager int  Optional//The id of a draft area containing files for this feedback.
} 
advancedgradingdataDefault to "Array
(
)
"//advanced grading data
object {
guideOptional//items
object {
criteria list of ( 
object {
criterionid int   //criterion id
fillingsOptional//filling
list of ( 
object {
criterionid int   //criterion id
levelid int  Optional//level id
remark string  Optional//remark
remarkformat int  Optional//remark format (1 = HTML, 0 = MOODLE, 2 = PLAIN or 4 = MARKDOWN)
score double   //maximum score
} 
)} 
)} 
rubricOptional//items
object {
criteria list of ( 
object {
criterionid int   //criterion id
fillingsOptional//filling
list of ( 
object {
criterionid int   //criterion id
levelid int  Optional//level id
remark string  Optional//remark
remarkformat int  Optional//remark format (1 = HTML, 0 = MOODLE, 2 = PLAIN or 4 = MARKDOWN)
} 
)} 
)} 
} 
} 
)