This is the case when some other plugin or theme has used bp_use_legacy_activity_query filter. The issue is has_more_items doesn’t get set in the return array of BP_Activity_Activity::get( $args ) call when above filter is used.
Is this a bug or we are missing something in our plugin/theme?
I know we can use bp_activity_has_more_items filter and look for $activities_template global variable but it doesn’t have all the required data to figure out whether it has more items or not.