The heavily hinted implication is that device use damages relationships. But look at what they actually measured. They ask adolescents to answer questions like:

"My primary caregiver ignores me when they are on a device." (DAIS, their new scale)

And then also ask them to answer questions like:

"I often worry that this person doesn't really care for me." (ECR-RS)

And then act like it's a revelation that these two self-report scales are correlated.

A much more plausible causal explanation is that a single psychological variable (e.g. a bad relationship) causes both self reports, rather than the implied pathway that device use causes A, which then causes B.