I contacted Winexpert, asking why 2 yeast are added. I usually get a reply back within a few days, although the holidays may delay that.
I asked WinExpert this very question back in 2020 and received the following reply:
"In our internal tastings we bench trial different yeasts and a couple of those are combinations. EC1118 is generally included in kits to ensure full fermentation within our timeline as it is a workhorse yeast. Other yeasts like RC212 or K1V are used for aromatics. We found certain wines benefited from a second yeast. We also work within an instructional timeline and different finished alcohol for our kits. Some wineries might use two different yeasts and blend after fermentation. This does not work with kits. There are differences between fresh grape winemaking and kit winemaking.
Hard evidence is in the bench trials for us. If the winemaker feels the flavors and aromatics are on target then that is the one used. There is a bit of an art to winemaking, as well."