Not sure whether it's a bug or a feature but when you have 2 Text Input
(Multiple) fields linked together, for example name & telephone number, with the
“Link this field to it’s sibling” feature, and both have the “Require a response
for this Field” enabled, only the second field is actually required for a
successful form submit.

In this example you could leave the name empty as long as you fill out a
telephone number. What you'd expect in this case is to have both name and
telephone number filled in before you can submit.