Wine using 200% CPU to run Might and Magic 6: Mandate of Heaven

I’ve installed MM6 using this guide, with the only differences that I’m using a virtual desktop size of 2400×1800 and recent versions of everything:

• Ubuntu 20.04
• PlayOnLinux 4.3.4
• Wine 5.0
• GrayFace MM6 Patch v2.4

The game works fine, but uses 200% CPU even when on the intro screen. Why would it use such a huge amount of CPU, and are there any simple ways to improve the situation?

A Wine debug session showed nothing obvious, but then I’m not an expert.