I'm not that up to date on hairpin lace, but the pictured stitch reminds me of a mile-a-minute afghan design worked in the round on both sides of the starting chain, then in the last round, the hook is inserted in each of the st and a long loop drawn up. After finishing off that loopy round, the loops are woven together 3 at a time.
All Needful Things
"Knit on, with confidence and hope, through all crises." Except carpal tunnel.
- Elizabeth Zimmermann