Punnet squares only represent the possibility of a potential pairing so in theory a 100% het x 100% het means you would have a 1 in 4 chance of hitiing a visual morph then the other 3 out of 4 represent the potential.for the other snakes.2 of the 3 should hold the gene while the other does not hence 66% (2 out of 3) this is true for both genes so it 66% het x2 so yes statistically you would have less of a chance of inheriting both genes but its just much easier to say 66% double het meaning a non visual morph from 2 100% hets. I hope my rambling made sense and was somewhat helpful.