Hi,
Thanks for posting!
NCrunch uses Gallio for Xunit integration under the hood, and the integration between these frameworks currently doesn't support the identification of nested Xunit tests while using static analysis. To work around this, you can change the 'Framework utilisation type for Gallio/Xunit' under your solution settings to 'UseDynamicAnalysis', though note that this will likely have an impact on the processing speed of NCrunch.
Cheers,
Remco