Dr. McCormick's description from his OsteoNaturals shop is the best explanation I've been able to find.
You can read it directly on his site, or at the end of this comment where I've cut and pasted it.

OsteoNaturals Osteo Collagen Pep:
https://www.osteonaturals.com/product-page/copy-of-osteo-collagen-pep-unflavored-450-grams
Here's the direct link to the randomized control study on Fortibone:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793325/
Be aware that the study was funded by the manufacturer of Fortibone.

The description on Dr. McCormick's site reads as follows:
"OsteoCollagen-Pep (Fortibone by Gelita) is unique among collagen products as it not only provides amino acids for collagen synthesis, but due to a highly controlled hydrolyzation process in its manufacturing that preserves specific Bioactive Collagen Peptides, this product has been shown to promote bone building activity.(1) Not only is OsteoCollagen-Pep 100% Type 1 collagen (the best at promoting improved bone health) but approximately 10% is absorbed intact as single helical, 5kDa amino acid polypeptide chains. These chains consist primarily of repeating glycine, proline, and hydroxyproline amino acids providing favorable folding and stability to facilitate absorption through the gut wall. These intact polypeptide chains then bind directly to receptor sites on bone-buildig osteoblasts while the other 90% is broken down into amino acids providing substrate for the osteoblasts to build bone.
In a 2017 study of 131 postmenopausal women, just 5 grams (one scoop) a day for one-year increased P1NP (a bone formation laboratory biomarker), and improved bone mineral density in the spine by 4% and in the femoral neck by 7%. By providing the basic amino acid building blocks for quality bone formation and Bioactive Collagen Peptides to stimulate osteoblasts to build bone, OsteoCollagen-Pep provides a dynamic one-two-punch that epitomizes OsteoNaturals' slogan: Where Bone Strength Begins.

1) Konig, D., et al. Specific collagen peptides improve bone mineral density and bone markers in postmenopausal women--A randomized controlled study. Nutrients. 2018.

* These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease."