Asynchronous REXX does not seem to work

From help:
'&&' as the last argument requests that the script be run asynchronously in the background.

my 'hello.rex':
say time() 'Hello world (from ooREXX)'
if arg(1)<>'' then say 'parms:' arg(1)
else say 'no args'

Screen clip:
HHC01603I exec hello.rex kilroy was here &&
15:35:38 Hello world (from ooREXX)
parms: kilroy was here &&       
 

 The double ampersands are sent to the rexx pgm as part of the parameter.