Safari throws exception when calling requestStorageAccess

I have to say Safari's (webkit) implementation of Intelligent Tracking Protection (ITP) and the Storage Access API has been challenging to get right.

Situation:

• We have a company that has grown through acquisition and we are trying to implement a unified authentication scheme that uses cross-domain access to tokens stored in cookies
• Each portal implementing the scheme will have an iframe that hosts a component from an authentication domain and will use postMessage() to check for the existence of the necessary authentication token.
• The initial implementation worked for Chrome/Edge/Opera/other Chromium browsers, but needed to be adjusted to implement the Storage Access API to allow the authentication component to request 1st party storage access.
• This worked as documented in Firefox
• Safari throws an exception when requestStorageAccess() is called and the error object is undefined

Here is some examples of the relevant code:

Iframe

<iframe  class="portal-navigation-frame" allowtransparency="true"
  style="position:absolute; top: -60px; right: -250px;display:none;"
  id="authFrame" 
  sandbox="allow-scripts allow-storage-access-by-user-activation 
  allow-same-origin allow-top-navigation allow-forms"
  src="@Constants.AuthenticationUrl"></iframe>

Authentication Component

const authorizeStorageAccess = async () => {
  if (document.hasStorageAccess) {
    try{
      if (await document.hasStorageAccess() == false) {
        console.log("authCommunicationService.authorizeStorageAccess", "does not have storage access");
        if (document.requestStorageAccess) {
          await document.requestStorageAccess();
        } else {
          console.log("authCommunicationService.authorizeStorageAccess", "requestStorageAccess not available");
        }
      }
      else {
        console.log("authCommunicationService.authorizeStorageAccess", "already has access");
      }
    }
    else {
      console.log("authCommunicationService.authorizeStorageAccess", "already has automatic 
  access");
    } catch (err) {
      console.log("authCommunicationService.authorizeStorageAccess", "error", err);
    }
  }
};

Note: authorizeStorageAccess is called from a button event handler and only after the user has been redirected to the authentication domain to login and returned.

Any assistance would be greatly appreciated.

Jason