As far as I can tell, the Points To Line GP tool can’t be used to create multi-part polylines:
Points To Line GP tool
ASSET_ID PART_NUM VERTEX_NUM X Y M
---------- ---------- ---------- ---------- ---------- ----------
001 1 1 0 5 0
001 1 2 10 10 11.18
001 1 3 30 0 33.54
001 2 1 50 10 33.54
001 2 2 60 10 43.54

Could support for multi-part features be added?