I don't understand this change. This means we'll call `seqToRepeatedChecked(optionTArg)` with `optionTArg =:= Product1[?T]`, but `seqToRepeatedChecked` is the identity for types that don't have `Seq` as a baseclass, and `Product1` doesn't inherit `Seq`.

I think the right solution is to make unapplySeq v unapply the top-level in the decision tree.

Closing this PR and submitting a fix along those lines.