Constant CPU usage by nightly flatpak version of GNOME Calendar while idle

Testing with my ThinkPad X220T laptop (with Intel Sandybridge Core i5 CPU and Intel graphics) on Xorg on Fedora 37, GNOME Calendar, whether version 43.1 or the nightly flatpak, constantly consumes 4 to 10% of the CPU even when it's been idling for a while and seemingly doing nothing at all. In this screenshot of the tophat gnome-shell extension, you can see the CPU usage graph used constantly in the 3rd quarter while gnome-calendar is running, and it drops to zero in the last quarter after gnome-calendar has been stopped:

Attached is a sysprof capture of the nightly version of GNOME Calendar: gnome-calendar-nightly-2023-02-20-idle-profile.tar.xz