Some tags are highlighted, some are not

I think the difference is one the tags are on handles on the layer (see the number "4" on the layer? that shows the layer has 4 handles added), the other the tags are on the layer itself (the origin marker) rather than a handle added to the layer.

Tagging layers rather than handles on layers does behave differently at times. E.g. a dragger via a handle will cause different stretching than putting it on the original marker. When looking for a tag such as "Head" which has children tags that it looks for, it should be on the layer origin. If you add a Head tag to a handle on a layer, it won't find children (handles don't have any children) - that one should be on the layer itself. (If you single click on a handle like elbow you would see the tags on that handle)