I am the NEON scientist responsible for the LAI Digital Hemispherical Photo data product and apologies it has taken a few days to see your question! The short answer is that NEON does not offer an LAI number derived from the photos. Although an actual LAI product was initially envisioned, it was descoped in consultation with NSF during the NEON construction period due to budget and schedule constraints. However, I have worked extensively with the European GBOV group to derive LAI from all the photos we collected between 2013 and 2017 (if I recall correctly), and these LAI numbers are posted for free on the GBOV Copernicus page: https://gbov.acri.fr/dataaccessLP/ ; a publication related to this work is currently in review at Remote Sensing of Environment.
If you download the same images that the GBOV group has analyzed, you should be able to compare and see how the numbers derived from your script compare with those derived by another group using the same input images.
Hope that helps!