"Missing" CSS properties Bug or Missing Functionality?

Although the (javascript) CSS Style object in Shotcut has the property “webkitTransformStyle”, setting its value to " preserve-3d" has no effect, the property acts as if its value is “flat” in all instances I have tried.

Is this a bug, or just functionality that is missing from the version of the HTML rendering engine that Shotcut uses?

Similarly the property “webkitBackfaceVisibility” ignores the setting of “hidden”, acting as if its value is always “visible”.