powershell - Host.ui.prompt doesn't pop up a dialog/form when run from the ISE

Question

I have a simple PowerShell script that uses both $host.ui.Prompt and $host.ui.PromptForChoice. When I run it from the ISE, PromptForChoice pops up a dialog but Prompt prompts at the console.

Read-Host also prompts at the console and does not show a dialog.

I.e. the script below shows a dialog for the initial choice, then prompts at the console pane for both A and B. Is this normal? My reading of the documentation suggests all three should throw a dialog. Have I missed something?

I'm running PowerShell 3.0 in case that's relevant.

$choicedesc = New-Object System.Collections.ObjectModel.Collection[System.Management.Automation.Host.ChoiceDescription] 
$choicedesc.Add((New-Object "System.Management.Automation.Host.ChoiceDescription" -ArgumentList "&Foo"))
$choicedesc.Add((New-Object "System.Management.Automation.Host.ChoiceDescription" -ArgumentList "&Bar"))
$choice = $Host.ui.PromptForChoice("Choice", "Make a choice", $choicedesc, -1)


$a = Read-Host "A"

$fields = New-Object "System.Collections.ObjectModel.Collection[System.Management.Automation.Host.FieldDescription]" 
$f = New-Object System.Management.Automation.Host.FieldDescription "B"
$f.DefaultValue = ""
$f.Label = "&B"
$fields.Add($f)

$result = $Host.ui.Prompt('cap','msg', $fields)