Alexa can't control Mini Split heat temperature through SmartThings + Cielo

I turned on the heat for the first time since installing a mini split and discovered that Alexa can’t change the heat mode temperature through SmartThings, although it can change the Cool mode temperature just fine.

Devices:
Samsung Hub, firmware version 000.054.00013, controller version 2.3.41-17
Cielo Breez Plus, Cielo App version 5.9.0
Pioneer mini-split, installed a couple months ago

To illustrate:

Me: “Alexa, set the mini-split to Cool.”
Alexa: “It’s set to Cool.”
Me: “Alexa, set the mini split to 70 degrees.”
Alexa: “The AC is set to 70.”
Me: “Alexa, set the mini-split to Heat.”
Alexa: “It’s set to Heat.”
Me: “Alexa, set the mini split to 70 degrees.”
Alexa: “That command doesn’t work on device Mini Split.”

I deleted and re-detected the Mini Split in the Alexa app. No change.

I can control both heat and cooling through the SmartThings phone app, although even in Heat mode, the set temp is called “Cooling temperature” in the SmartThings UI.

What is going on here? Why can I set a Cool temp but not a Heat temp from Alexa? Is there some workaround that will let me control the heat temperature setting?

Thanks,
Mark

One workaround is to remove the Cielo link from SmartThings and add the Cielo skill to Alexa, i.e. bypass SmartThings for this device. That does allow controlling the Heat temperature, but it sort of defeats the idea of having a SmartThings hub as the central controller of the smart home.