MariaDB Columnstore produces wrong averages on extracted null-datetime fields (like year)

See the code attached.

Averaging over YEAR of a datetime-column that contains null-values gives 999.999 as average.

Only happens with Columnstore, InnoDB does everything correctly.
Occured on EBI03. No other server tested so far.

also affects MariaDB Version 10.6.9 CS Version 6.4.3

TODO: Interesting: does the error also occur on other functions, say, length of strings?
UPDATE: no, using length function on varchar fields does NOT show the error, attached the second SQL file for demonstration.