Does this rule of thumb always apply? Is it a guideline I should try to stick to once I start breeding? I understand the logic behind it, but if I have the opportunity to add an amazing single-gene male to my collection (GHI, OD, Black Head, etc), is there any reason I shouldn't want to add him in to the plan simply because he would only be a single-gene male being bred with my two- and three-gene females? Or, am I interpreting the guideline too narrow-minded and "genetically greater" may actually mean "more desirable", thus answering my own question?

Thanks for your insight in advance!