Formula Twins (exact-twin / near-twin)
Our term for a cluster of products sharing an identical formula across multiple brands. An "exact-twin" cluster requires every compound, form, rounded elemental amount, and serving size to match precisely; a "near-twin" cluster relaxes that to just compound and form, ignoring the exact declared amount.
Example
3,699 exact-twin clusters cover 15.3% of on-market products; loosening the match to near-twin raises that to 25.9%.