I don't really follow what the product rule controversy is all about. The product rule is correct if the variables or events are independent. IIRC, in People vs. Collins one of the reasons that the conviction was thrown out by the appeals court is that the state didn't show that independence. Was that the issue in Casias?

No. I linked the case, you can read what the issue was. The state didn't lay foundation for how the statistical conclusion was arrived at, i.e., there is no testimony that the product rule, or some other methodology, was used.

FN2 in Casias implies that there will not be an issue of admissibility if the product rule is used, period. That there is no need to demonstrate or show evidence the accumulated probabilities/variables are independent.

I'm not positive where Mantei is going, unless it is simply to show that the product rule is allowed in Fl, but has been scientifically discredited unless properly qualified (variable independence). So, if his expert is using something that is scientifically discredited, the testimony can still come in if the method can be valid in some applications.