I downloaded Sentinel-2 MSI L2A product for 17th Nov 2022 from Sentinel Hub, and converted DN values to reflectance, reprojected to EPSG 4326 and calculated NDVI in QGIS. I also downloaded raw data for Band 4 & Band 8 form Sentinel Hub EO Browser, and then calculated the NDVI in QGIS. Although the spatial variation is the same, there is a major difference in the values.
What could be the reason for this difference ? Is it some step in the preprocessing which is being missed ? Because as far as I know atmospheric correction using Sen2Cor won’t be required for this product since it’s already BOA, and there aren’t any other pre-processing steps for Sentinel Optical Data.