I see, so you're saying that that the ReSharper client appears to not work with a ODATA/v2 API? In this case, this is most certainly a bug or a misconfiguration and you should share/communicate it to JetBrains.
There is virtually no support in commercial or open source private repositories for JSONLD/v3. While it's on our roadmap to implement, it wouldn't come until late this year... and obviously it would require upgrading your PRoGet server software, which many organizations don't like doing for at least 6/12 months after a release (especially for something like ProGet).
So, this would effectively makes ReSharper unusable for private extensions.