According to this site:

By default, the commits are shown in reverse chronological order.

--date-order
Show no parents before all of its children are shown, but otherwise show commits in the commit timestamp order.

and this site:

By default, with no arguments, git log lists the commits made in that repository in reverse chronological order. That is, the most recent commits show up first.

It seems that the graph view date order option that the output from the command 'git log' with the default reverse chronological order not with the option '--date-order'.