App.close fails to close

1.1.0(2015-07-21_01:00nightly)/Mac10.10.4/Java8(64)1.8.0_25-b17

def Gen_Close_App():
    global Which_App
    App.close(Which_App)
    #closeApp(Which_App)
    print "Gen_Close_App() ",Which_App

Which_App = "Tuck"
Gen_Close_App()

Result :-
Gen_Close_App() Tuck

but app still running

Opening the App works fine :-
def Gen_Open_App():
    global Which_App
    App.open(Which_App);
    wait(1)
    App.focus(Which_App)
    App.open(Which_App);
    wait(1)
    App.focus(Which_App)
    print "Gen_Open_App() ",Which_App

Which_App = "Tuck"
Gen_Open_App()
result :-
[log] App.open [-1:Tuck]

[log] App.focus: [-1:Tuck]
[log] App.open [-1:Tuck]

[log] App.focus: [-1:Tuck]
Gen_Open_App() Tuck

I saw from reading instructions that the name needs to be the name in the Tool Bar - I presume that this means the name in the Dock
Tuck is the name in the Dock and also the name in Activity Monitor
I also tried the above with
          Which_App = "Google Chrome"
          Which_App = "Safari"

and failed to get it to close

is this a bug or am I doing something wrong

what is Tuck - Tuck is a Fluid Application - http://fluidapp.com/
Fluid allows you to load a specific web site