createUIDefinition.json: Error: Unknown function 'if'

Question

Testing createUIDefinition.json with https://github.com/Azure/azure-quickstart-templates/blob/master/sideload-createuidef.sh

The 'if' function described in the docs does not appear to work:
https://learn.microsoft.com/en-us/azure/azure-resource-manager/managed-applications/create-ui-definition-logical-functions#if

Specifically I am trying to return one of two strings in an output, starting with the example in the doc:

   "outputs": {  
        "myoutput": "[if(equals(42, mul(6, 7)), 'yes', 'no')]"  
    }

The error reported by the console:
[Microsoft_Azure_Compute] 3:58:11 PM MsPortalFx.Base.Diagnostics.ErrorReporter 3 MsPortalFx.Base.Diagnostics.ErrorReporter: message: Unknown function 'if'
Details: {"type":4,"function":"if","params":[{"type":2,"value":true},{"type":1,"value":"yes"},{"type":1,"value":"no"}],"path":[]}
stack: Error: Unknown function 'if'
Details: {"type":4,"function":"if","params":[{"type":2,"value":true},{"type":1,"value":"yes"},{"type":1,"value":"no"}],"path":[]}
at t.n.evaluate (https://afd.hosting.portal.azure.net/compute/Content/Dynamic/T4szTja92chj.js:12:768)
at t.n.evaluateToResult (https://afd.hosting.portal.azure.net/compute/Content/Dynamic/T4szTja92chj.js:12:1173)
at t.evaluateToResult (https://afd.hosting.portal.azure.net/compute/Content/Dynamic/T4szTja92chj.js:13:4188)
at https://afd.hosting.portal.azure.net/compute/Content/Dynamic/whMGwlab_Aoz.js:29:14428
at Array.forEach ()
at t._resolveTemplateParams (https://afd.hosting.portal.azure.net/compute/Content/Dynamic/whMGwlab_Aoz.js:29:14376)
at Object.supplyInitialData (https://afd.hosting.portal.azure.net/compute/Content/Dynamic/whMGwlab_Aoz.js:29:7723)
at Object.supplyParams (https://portal.azure.com/Content/Dynamic/1rEwFp4kIIC3.js:163:677)
at o (https://portal.azure.com/Content/Dynamic/1rEwFp4kIIC3.js:204:622)
at n.l [as callback] (https://portal.azure.com/Content/Dynamic/1rEwFp4kIIC3.js:204:990)
From RPC: fx -> Microsoft_Azure_Compute
(Callstack capturing is not enabled. Use ?trace=diagnostics to enable it.)