`delete()` vs. `fetch()` with underspecified relative restrictions

Question

My database has a number of sessions.

@schema
class Session(dj.Manual):
    definition = """
    -> Subject
    session_datetime: datetime
    """

I could fetch or delete them as follows.

total_sessions = session.Session # N=4
total_sessions.fetch()   # Successful output
total_session.delete()   # Successful cascading delete prompt

If I'm only interested in sessions after a given year/month, I can generate a query with a relative restriction, fully specifying datetime.

later_sessions1 = (session.Session & 'session_datetime > "2021-06-01 12:00:00"') # N=2
later_sessions1.fetch()   # Successful output
later_sessions1.delete()  # Successful cascading delete prompt 

If I don't fully specify datetime, I can still fetch the data, but deletion fails.

later_sessions2 = (session.Session & 'session_datetime > "2021-06"') # N=2
later_sessions2.fetch()   # Successful output
later_sessions2.delete()  # OperationalError: (1292, "Incorrect datetime value: '2021-06' for column 'session_datetime' at row 1")

Is this intended? Should fetch() and delete() fail under the same conditions?

---

EDIT: calling make_sql() on later_sessions2 returns the following

'SELECT DISTINCT `subject`,`session_datetime` FROM `test_session`.`session` WHERE(session_datetime > "2021-06")'

If called on the fully specified later_sessions1, the last WHERE component includes the full datetime.

Answer 1

Per comment thread above with Raphael and Dimitri, this is a quirk of MySQL rather than DataJoint