Calendar items sent to users have reminder as 15 minutes regardless of reminder_is_set set to False

[reziandoni]

item = CalendarItem(
account=a,
folder=shared_calendar,
required_attendees=["mary@example.com"],
legacy_free_busy_status = 'Free',
reminder_is_set = False,
is_response_requested = False,
allow_new_time_proposal = False,
reminder_minutes_before_start = 0,
)
item.save(send_meeting_invitations=SEND_TO_ALL_AND_SAVE_COPY)

when I create a shared calendar and send it to users with the above example:

1. on the shared calendar the reminder is set to None
2. on user's calendar I see the reminder still set for 15 minutes.

Is this a bug or something that I am doing wrong?

[reziandoni]

This happens if reminder_minutes_before_start is set. Otherwise this works as expected.