Doubt that to be true to any significant degree. The vapor chamber helps the heat spread throughout the body of the device, but the heat then has nowhere to go because it hits layers of rubber and plastic. With no where to go, you saturate the phone very quickly with heat as it can't dissipate well. And I highly doubt it runs any cooler than an iPhone built like the 16 Pro with a vapor chamber would have, which is very clearly the optimal construction of a premium phone: vapor chamber, aluminum internal chassis (like the 16 pro), titanium outer shell (like the 16 pro). And also like premium Android flagships.
The aluminum is a cost-saving measure, and the lipstick on the pig is the thermal marketing. Especially considering a thermally-insulating case is required to prevent normal wear and tear from making the phone look like trash.