"Costs [amount] [stockpiledResource]" not working for improvements

[SpacedOutChicken]

Is there an existing issue for this?

• I have searched the existing issues

Game Version

4.14.3

Describe the bug

Adding "Costs [amount] [stockpiledResource]" to an improvement doesn't do anything. It does not prevent a tile improvement from being built if resources are too low, and once built, the amount of stockpiled resource never goes down.

Steps to Reproduce

If you create a stockpiled resource, the uniques say that you can attach a cost to improvements, just like you can to buildings and units, but the cost doesn't take effect on improvements.

Screenshots

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Link to save file

No response

Operating System

Windows

Additional Information

I've been able to get the effect I want by combining "Instantly consumes [amount] [stockpiledResource]" and "Only available <when above [amount] [resource]>" but I would prefer to use the unique that should be doing both jobs at once.