Currently the help popup for the new assignment activity setting 'Require that students accept the submission statement' is:
Require that students accept the submission statement for all assignment submissions for this entire Moodle installation. If this setting is not enabled, then submission statements can be enabled or disabled in the settings for each assignment.
which is only suitable for the admin setting for all assignments (in Settings > Site administration > Plugins > Activity modules > Assignment ).
As the admin setting for all assignments works rather differently from the assignment activity setting, I suggest we have different lang strings, using requiresubmissionstatement_help for the assignment activity setting and requiresubmissionstatement_desc for the admin setting (as recommended in the dev docs http://docs.moodle.org/dev/Help_strings ).
For requiresubmissionstatement_help I'd suggest:
'If set to yes, students must tick a checkbox to accept the site-wide submission statement before they can submit their assignment.'
For requiresubmissionstatement_desc I'd suggest:
'If enabled, students are required to accept the submission statement for ALL assignment submissions site-wide. Otherwise each assignment activity includes a "Require that students accept the submission statement" setting.'