The form datetime selector defaults hardcodedly to 5 minute steps. If you need to change that default throughout the Moodle forms, you need to hack around line 83 in /lib/form/datetimeselector.php
$this->_options = array('startyear' => $calendartype->get_min_year(), 'stopyear' => $calendartype->get_max_year(), 'defaulttime' => 0, 'timezone' => 99, 'step' => 5, 'optional' => false);
and change the 'step' value to 1.
hth
I can confirm your observation but the behavior is inconsistent with other activities and in itself doesn't make much sense. As such is very likely an unintended bug and should be reported in the tracker unless already reported.
An activity appears in the gradebook only if you assign it a grade (in the activity settings). The default for new activity used to be no grade to the effect that the activity did not appear in the gradebook unless you specifically assigned a grade to it. But since a certain Moodle version the default is point 100 scale, although it is site configurable and can be turned off. Indeed the new behavior may be confusing if you are not aware of it because the activity grade setting is typically hidden in the settings form under the Grade fieldset and you have to open the field set to see it. hth
In the Dataform (2.9 onward) peer reviewers can use the same rubric that the instructor uses for grading the activity. In fact, they can use more than one rubric in the same activity. And then you can send to the gradebook any of the completed rubrics or none. So, you can include the peer reviews in the activity grade if you want to.