Just like the image contrast at the film plane will be lower due to flare, so will the image contrast on the paper be lower due to enlarger flare. Although the paper LER for grade 2 is right on 1.05, an NDR of 1.05 will not at all compensate for any loss due to enlarging flare. So, bumping the aim NDR up to 1.2 compensates for at least a half stop loss of contrast due to flare losses at the enlarging stage---------a full stop loss of contrast at the enlarging stage would require an NDR of 1.35. But I've no idea exactly what the flare loss is from the enlarger, but bumping the aim NDR up by some amount to help compensate for it is probably wise.