ID 553128 - Transform node motion blur is not applied if a Python expression is used

Problem summary:
Transform node motion blur is not applied if a Python expression is used
 
Customer reported version:
Nuke 13.2v5
 
Customer reported platform:
macOS 11 Big Sur
 
Steps to reproduce:
1) Launch Nuke and create a ColorWheel node in the Node Graph.
2) In the Properties panel, change its format knob to square_256.
3) Create a Transform node.
4) Click the translate knob's Animation Menu and select Edit Expressions... 
5) Enable the Py button, then paste the following expression into the x and y fields: nuke.frame()*100
The Transform1.translate window should now look like this:

6) Click OK to confirm the Python expression, then create a Merge node and a CheckerBoard node.
7) Merge the Transform node over the Checkerboard and View the result.
8) In the Transform node's Properties, increase the motionblur knob to 1 (or greater), and observe how no motion blur is applied:

 
Expected behavior:
The Transform node's motion blur option should function regardless of what animation or expression is used on the node's knobs.
 
Actual behavior:
Using a Python expression to drive a Transform node does not allow the Transform node's motion blur to work as expected. However, Nuke/TCL expressions do seem to work correctly:

 
Workaround:
No known workaround at this time
 
Reproduced by Support in:
Nuke 14.0v5 - Windows 10, CentOS 7
Nuke 14.0v1 - Windows 10
Nuke 13.0v1 - Windows 10
Nuke 12.0v1 - Windows 10
Nuke 11.0v1 - Windows 10
Nuke 10.0v1 - Windows 10, CentOS 7
 
Earliest version tested:
Nuke 10.0v1 - This issue appears to be in all tested versions of the product