Unsure if this is a bug, or intended behaviour, but when copying an essential property and pasting onto other layers that share the same essential property, that value doesn't get pasted. Similarly, when copying an expression only from an essential property, it's also not pasted when other layers that share that property are selected.
The workaround for this is to select that property on each layer (rather than selecting the layer itself) before pasting. This is quite inconvenient, and doesn't follow the convention for other property types.