Not sure, as Impromptu.InvokeConstructor is specifically for dynamic usages, it's a different use case that the generic CreateInstance. Anyway this functionality is soon to be obsoleted as it's been moved to the Dynamitey project as Dynamic.InvokeConstructor
Isn't this slower than http://stackoverflow.com/questions/2024435/how-to-pass-ctor-args-in-activator-createinstance-or-use-il