Possible In-memory repository regression?

So I'm trying to get my branch updated with master https://github.com/Zoxive/libgit2sharp/tree/zoxive/refdb/ which revives the pluggable RefDb backend (#1226)

I've gotten through all the compile issues rebasing it up to the latest with dotnet core, and the codegen stuff. (Took a while to figure out that I had to change all the NativeMethod funcs to use the new custom marshaler)

Anyways all compiles and stuff now.. but testing my changes im running into an error that appears to be coming straight from libgit2.

LibGit2SharpException: path cannot exist in repository

It happens when i have an in memory repository and an OdbBackend.

Heres a sample unit test that shows the problem.
https://github.com/Zoxive/libgit2sharp/commit/7957581353134c17deaa71714ffd24a0a6130c5e

I did see that libgit2 had a regression (https://github.com/libgit2/libgit2/pull/4263) @ethomson fixed.
I'm guessing its related?

Start by running the sample unit test in commit 7957581353134c17deaa71714ffd24a0a6130c5e with an in-memory repository and an OdbBackend. Compare the failure with libgit2 pull request 4263 and trace where the “path cannot exist in repository” exception is surfaced. Done means the reproduction passes without regressing other repository backends.