Offhand I don't know why it copies PYD and DLL files from the DLLs directory. It's part of the standard library. The virtual environment should only need to copy or symlink the binaries in the application directory, such as python.exe, pythonw.exe, vcruntime<###>.dll, python<##>.dll, and python<#>.dll. Currently a virtual environment doesn't use the binaries that get copied or symlinked from the DLLs directory, since the system DLLs directory is in sys.path.

Also, why does it copy over init.tcl? _tkinter uses Py_GetPrefix() to to get the real prefix directory in order to find the TCL library at "tcl\tclX.y". For a Python 3.7 virtual environment, I verified using Sysinternals procmon that TCL loads the init file from "C:\Program Files\Python37\tcl\tcl8.6\init.tcl", not the virtual environment.