You can't target Win64 in shipping from the binary build.
When packaging your project for shipping, the windows 64 bit option will be grayed out.
I also tested this issue out in main (2455917) and the option is able to be selected but with the 4.7.2 (2467323), the option is grayed out.
1) Open a new template project in 4.7.2
2) When the project opens, Click on the file tab at the top of the Editor.
3) From the file tab, go to Package Project>Build configuration and change the option to shipping.
4) Open the file tab again, go to Package Project>Windows and you will see that the Windows (64-bit) option is grayed out.
Head over to the existing Questions & Answers thread and let us know what's up.