Inconsistent autowatch rerunning for Expecto test project

I have a workspace with two F# test projects: one xUnit (made with dotnet new xunit -lang F#) and one Expecto (made with dotnet new expecto). (This is using core 3.0.0 preview 9), with a new install of VSCode and .net test explorer on Win10.)

I have autowatch enabled, and it works as currently expected for the xUnit project: if I save a file in that project it reruns that project's tests.

But if I save a file in the Expecto project, it reruns all the tests in *both* projects. I would expect it to rerun only the tests in that one project.