What boggles the mind (not in this case where Ubi is involved) is why it must not be optional. This just goes along with the well known phrase by A. Einstein:
"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."
... provided that the feature and above report is true.
EDIT: Can we have the link to the thread/post luthier made at Sukhoi.ru forum? Thnx.