Classic approval notification changed to responsive with no configuration changes

Summary: We had Classic Approval notifications enabled and they were converted into responsive approval, but we did not make any configuration changes. This was happening in production only, but now we see it in our test instance as well, but not our development instance.

We did not have any patches applied at the time either.

Has anyone one else had a similar issue? If so, what did you guys do to resolve it?

Content (please ensure you mask any confidential information): Used to look like this:

Now it looks like this:

Version (include the version you are using, if applicable):