...
The main reason for this is that a lot of packages for the AEM API have changed their major version number (although not changed much technically, e.g. only because some deprecated features where removed).
AEM Mocks for AEM 6.2
There is a branch with a snapshot version of io.wcm.testing.aem-mock 2.0.0-SNAPSHOT compatible to AEM 6.2 and the latest Sling API changes and latest Oak version:
https://github.com/wcm-io/wcm-io-testing/tree/feature/aem-6.2-api
The 2.0.0-SNAPSHOT version is also deployed to Sonatype OSS Snapshot Repository.
Make your application compatible with AEM 6.2 API
...