I downloaded MOD09A1 data by MODIStsp package.
As we all know, the CRS of original MODIS data is Sinusoidal projection. And the resolution of MOD09A1 is 500m.
However, the results are not 500m.
I have tried different CRS parameter in MODIStsp GUI. But it is still not 500m.
For the MODIS Sinusoidal, the 463 meters are correct. It is close to 500m, not exactly 500m. You can check this document. NDVI The theory behind them are the same. For the CRS32649, as you reprojected the raster file, the resolution will change. Raster includes rows and columns, projection sometimes will change the resolution or values. Please be careful.