ProxyConfiguration in WKWebView doesn't allow trusting self-signed certificate

I have an HTTP3 relay setup and I'm trying to get WKWebView traffic to use it. The relay has a self-signed certificate for TLS traffic.

When using URLSession to make a call, everything works as expected, but in WKWebView, it doesn't.

Here is how I setup my ProxyConfiguration

let options = NWProtocolTLS.Options()
// sample options to trust any certificate for testing
        sec_protocol_options_set_verify_block(options.securityProtocolOptions, { (sec_protocol_metadata, sec_trust, sec_protocol_verify_complete) in
            sec_protocol_verify_complete(true)
        }, DispatchQueue.global())
        
        let relayServer = ProxyConfiguration.RelayHop(http3RelayEndpoint: relayEndpoint, tlsOptions: options)
        let relayConfig = ProxyConfiguration(relayHops: [relayServer])

I connect that to my webview by simply doing the following:

let configuration = WKWebViewConfiguration()
        configuration.websiteDataStore = WKWebsiteDataStore.nonPersistent()
        configuration.websiteDataStore.proxyConfigurations = [relayConfig]
        
        let webView = WKWebView(frame: .zero, configuration: configuration)

The sec_protocol_options_set_verify_block is never called for the WKWebView (it is when I use URLSession)

I get the following error in XCode

[pageProxyID=7, webPageID=8, PID=73105] WebPageProxy::didFailProvisionalLoadForFrame: frameID=1, isMainFrame=1, domain=NSURLErrorDomain, code=-1202, isMainFrame=1, willInternallyHandleFailure=0

Is there some API I am missing to get the webview to do custom TLS validation with an HTTP3 relay?