SNAP does not fully read the Sun/View Zenith/Azimuth grids.
The grids have a size of 23x23 but SNAP shows only 22x22.
The last row and last column are omitted.
This happens for L1C and for L2A data
Also, I think it would be good if the grids would be added as tie-point grids. Then they would be automatically interpolated for users.