The recommended test methodology for SCIM is described in this section of the SCIM Provisioning with Lifecycle Management (https://developer.okta.com/standards/SCIM/#step-2-test-your-scim-server) article.
To answer your question regarding the Okta Provisioning Connector Tester tool - I have not found any reference in our documentation, internal or customer facing, that it supports SCIM 2.0 specifically, nor have I found anything on our Roadmap regarding a new version of the tool.
If you would like to get more information regarding the tool and suggest it be updated to support SCIM 2.0 then I recommend opening a case with our Dev Support Team by emailing firstname.lastname@example.org .
Technical Support Engineer
Okta Global Customer Care