I don't know if I am overlooking but if I am right, the assemblies are being loaded twice during the discovery of assembly parts.

Please see: https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNetCore.Mvc.Core/Internal/DefaultAssemblyPartDiscoveryProvider.cs#L37-L38