The checkpoints page in Hyper-V Manager has an option called Use automatic checkpoints.
What does that option do?
I can't find any mention on MSDN:
It seems that:
Use automatic checkpoints will create a checkpoint when your VM starts (iff there is no existing checkpoint) and delete it when your VM shuts down cleanly.
Via a question about disabling this feature, on ServerFault, an no-longer-online 2017 Microsoft article, Making it easier to revert:
Starting in the latest Windows Insider build, you can now always revert a virtual machine back to the state it started in.[...]
[...] when you start a virtual machine that doesn’t have any checkpoints, we create one for you so that you can easily roll back to it if something goes wrong, then we clean it up once the virtual machine shuts down cleanly. [...]
Note: the checkpoint will only be taken automatically when the VM starts if it doesn’t have other existing checkpoints.
This is corroborated by an unaffiliated blog post Hyper-V Checkpoints Best Practices:
If you have selected Standard checkpoints, you can enable the feature of Automatic checkpoints, which automatically takes checkpoints of VMs when they’re started and deletes them as soon as they are stopped.