[gliese1337]

In fact, let's go ahead and just look at the actual Conclusion section:

    To conclude, here, we showed that mask use influences our ability to infer facial expressions at any age.

Yes, duh. We're not good at it anyway. (They claim that people are doing good when they get above 66% of judgments correct--still a D grade.)

    Furthermore, we showed that the human capacity to read emotions from facial configurations when a face mask is present becomes particularly reduced in toddlers. We suggested that this is related to different age-related developmental stages of face processing associated with emotional reasoning.

Yeah, not surprising. But toddlers still get most of their social input from their families, so the most impacted group is also the group we need be least concerned about.

    Such observation poses the question whether a privation of facial visual features, as the one we are experiencing due to the COVID-19 pandemic, might alter or delay the development of social skills associated with face perception in early childhood.

It poses the question. That's it. They have no evidence that there actually is any alteration to social skills, and no evidence that that would be a bad or disabling thing if there were.

    Designing devices for personal protection that allows visibility of the lower part of the face may be crucial in all environments important for developing social and interaction skills in children, such as in education or rehabilitation, especially for those suffering from sensory or cognitive deficits.

Sure, that seems like a good idea. But it's not an excuse to not wear a mask if you can't get a transparent one.

    Knowledge from the current study can inform emotion-centered interventions and prevention programs that aim to foster socio-emotional processes linked to emotional understanding (Izard et al., 2008).

Yes, it absolutely can.

So, that's what it actually says. It very clearly does not say that kids will be psychologically damaged by not being able to see the lower halves of other people's faces in public, and it does not make any attempt to account for social learning in the home.