Dowitcher at lake Tutchewop

dear birders, I know there has been a lot of discussion about the species of Dowitcher at lake Tutchewop. The literature (e.g. https://www.aba.org/birding/v37n4p380.pdf ) suggests that Long-billed typically moult out of breeding plumage on migration in July to October whereas the Short-billed arrives in the wintering ground and then moults. Does any one have an explanation as to why this bird has completed its migration (albeit in the wrong place) but is still very finely dressed in it’s breeding plumage? regards Peter Marsh