The real meaning is we don't provide a Visual Studio plugin to develop 64bit pbx.
If you had a 64bit pbx, it should work in 64bit PB applications. However, because PB IDE is 32bit, you can't use a 64bit pbx at design time. Thus, you use a 32bit pbx in PB IDE to develop, deploy as 64bit app and run the app with a 64bit pbx.
You can see in your PB IDE installation folder that we ship three pbx files in 64bit: pbdom, ejbclient and wsclient.
Yes, 64bit and 32bit are same in most functionnalities and behaviors.