NB 8.2 What is the difference between app.exe and app64.exe when you use a 64 bit JRE ?

I see when building my RCP app I get an app.exe and an app64.exe.  As much as I know is the app.exe a x86 and the app64.exe an amd64 build executable. 

Now launching my RCP with app.exe or app64.exe results in the same where Help-> About tells me the system is using teh 64 bit JRE whichj I have bundled with the RCP app.

Question:  What's the difference using app.exe vs app64.exe in this situation running on a 64 bit Win 7 box ?