Hi,
the device detection is independent of the User agent,
that means even when the User agent is set to iPhone the viewer will
still detect that it is running on Desktop,
internally the 'navigator.platform' setting of the browser is used for that,
this setting will be always the same, regardless of the User agent,
and I don't know if it's possible to change that too in Safari...
but I understand what you want to do - I will add a switch to enable
testing a certain device,
best regards,
Klaus