That's because of the unfortunate and common misunderstanding in the ball python community of what the word heterozygous means. Hets are only normal looking with recessive mutations. Heterozygous really means having an unmatched pair of genes. Understanding that the pastel has one pastel mutated copy and one normal for pastel copy of the genes at the pastel locus makes it easy to understand that it a has a 50/50 chance of passing the pastel mutant version on to each of it's offspring.
As combinations involving different mutation types become more common I think it's worth the time to go back and understand genotypes as it will make predicting outcomes much easier.