Not sure this will end discussion or not, but it’s well understood in the scientific community that there can be incomplete expression of recessive genes in the heterozygous form. This has been studied in mice (citations given but not really for the casual reader: https://academic.oup.com/hmg/article/7/6/945/2896770) and human diseases (https://tinyurl.com/3azbtbmm, HEREDITARY BLINDNESS AMONG PINGELAPESE PEOPLE OF EASTERN CAROLINE ISLANDS - ScienceDirect).
The genetic origin of piebaldism in ball pythons has been identified and the cause is different than in mammals (in mammals it’s a neural crest disorder, https://www.biorxiv.org/content/biorxiv/early/2020/11/01/2020.10.30.362970.1.full.pdf).
Although no peer-reviewed literature exists that I can find that discusses incomplete expression of piebaldism and other “recessives” in ball pythons, such distinctions seem to be more of a terminology issue in the hobby rather than a truly scientific debate. Incomplete expression can be sometimes used interchangeably with incomplete dominance; the allele for the “recessive” morph is considered recessive, the “dominant” allele is the “normal phenotype” allele. Depending upon the genetic makeup of the individual, if the “normal phenotype” allele is affected in some way by other alleles on a chromosome, incomplete expression of a typically recessive trait could occur.
We have a tendency to think that each allele is fully independent of other alleles when we discuss recessive traits in ball pythons. However, we know alleles interact with each other, sometimes creating crazy results, especially in plants (such as totally new alleles in corn: https://academic.oup.com/genetics/article/135/3/881/6011312?login=true, or abortion of gametes in tomatoes: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1211010/pdf/85.pdf). For some reason this confusion doesn’t exist when we discuss codominant traits, although the mechanisms are the same. For example, we know fire interacts with yellowbelly to create fire yellowbellies that look different from each individual morph, we know that the different blue-eyed leucistic and black-eyed leucistic morphs create different looking homozygous animals, etc. The examples of allelic interaction are endless, it’s literally the basis of the hobby.
It’s reasonable (in fact, I believe it is accurate) to assume that traditionally “recessive” genes can also be affected by allelic interactions, especially when one or more morphs are at play. It’s likewise reasonable to assume the ‘strength’ of that incomplete expression of a typically recessive trait will naturally vary by how it interacts with other alleles. Please refer to my post above with how these codominant genes interact with a single piebald allele and results in an incomplete expression of that piebald allele, but in short, we know het pieds can create ringers, dorsal stripes, reduced patterns, and lighter colors in morphs such as cinnamons, lessers, yellowbellies, etc.
That all said, I’m not sure it matters whether we label piebald as recessive. The snakes don’t care, and you can’t get a piebald snake without both parents haven’t at least one copy of the gene. Be free, be merry, don’t get hung up on terminology, and have fun with the hobby everyone.