Happy to help, Wendelin,
Mind sharing additional details on how/where you came across this? Very possible we are not looking at the same thing.
Checked internally and can confirm the alias is still: Microsoft.ApiManagement/service/properties/displayName .
I don't see any alias for /service/namedValues...
PS cmdlet used:
$temp = Get-AzPolicyAlias -Namespace 'Microsoft.ApiManagement'
$temp.aliases | Where-Object { $_.Name -like 'displayName' } | Select-Object -Property Name
Looking forward to your reply.
Cheers.