From what I've been reading (e.g. this) I should be able to animate the scaling of a layer in Photoshop CC 2018's Timeline, provided the layer is a smart object. Once an object is a smart object the 'Position' option for that layer in the timeline should change to 'Transform'. Okay, that makes sense.
However, when I copy and pasted some artwork from Illustrator into Photoshop, I chose for it be pasted as a smart object. It has a 'Smart' icon in the layers panel. But examining that object in the timeline shows that it only has the 'Position' option, not 'Transform'. To make Transform available I have to select the layer in the Layer panel and choose 'Convert to Smart Object', sort of double-smartening it.
Why does vector artwork pasted as a smart object not gain full 'smart object' privileges without this doubling-up process?