API call from within APP not using App Proxy

I have a custom App and I am making a POST request inside of it. I have configured the App proxy with a Subpath prefix (apps) and Subpath (storepickup) The URL I am using is /Subpath prefix/Subpath/<API_END_POINT>

For example:

fetch("/apps/storepickup/updateshopifypluginsettings",
    {
        method: 'POST', 
        mode: 'cors', 
        cache: 'no-cache', 
        credentials: 'omit', 
        headers: {
            'Content-Type': 'application/json'
        },
 

In the App Proxy I have configured the Proxy URL to https://460xxxxxx.ngrok.io/storepickup

When the fetch is called the URL generated does not use the ngrok URL I have configured in the App Proxy but instead uses the App Set Up App URL (e.g: https://b0c0xxxxxx.ngrok.io/) so the generated URL I get is https://b0c0xxxxxx.ngrok.io/shopifypluginsettings when I should expect to get https://460xxxxxx.ngrok.io/shopifypluginsettings. Anyone know what is wrong?

Hey were you able to resolve this?