Read Prompt query string parameter in custom policy

Question

I am following this article to read prompt parameter from the url when signing in via custom policy in Azure AD B2C
https://learn.microsoft.com/en-us/azure/active-directory-b2c/claim-resolver-overview#openid-connect

I can read scope just fine, but when trying to read prompt the exact same way as scope in the same technical profile as I am doing the read from scope, prompt comes out empty.

TechnicalProfile Id="OIDC">
<DisplayName>Employee</DisplayName>
<Description>Login with account</Description>
<Protocol Name="OpenIdConnect" />
<Metadata>
...........
<Item Key="IncludeClaimResolvingInClaimsHandling">true</Item>
</Metadata>
....
<OutputClaims>
.......
<OutputClaim ClaimTypeReferenceId="scope" AlwaysUseDefaultValue="true" DefaultValue="{OIDC:Scope}" />
<OutputClaim ClaimTypeReferenceId="prompt" AlwaysUseDefaultValue="true" DefaultValue="{OIDC:Prompt}" />
</OutputClaims>