sentry-javascript: Using sentry hub doesn't send release health and performance metrics

Environment

SaaS (https://sentry.io/)

Version

• @sentry/browser => 6.3.5
• @sentry/react => 6.15.0

Steps to Reproduce

Description

We are using Sentry Hub because we have more than one project on each page with each using a different Sentry project. The errors for each project are reported properly but some metrics are missing

Steps

• Create a react sentry project
• Use the Sentry hub + Browser client to initialize Sentry and capture errors instead of using Sentry.init ie.

import {
  BrowserClient,
  Hub,
  reactRouterV5Instrumentation,
  defaultIntegrations,
} from '@sentry/react';
import { Integrations } from '@sentry/tracing';

const client = new BrowserClient({
    dsn: sentryDSN,
    release: appName,
    environment: ENV,
    integrations: [
      ...defaultIntegrations,
      new Integrations.BrowserTracing({
          routingInstrumentation: reactRouterV5Instrumentation(
            appBrowserHistory
          ),
      }),
    ],
    tracesSampleRate: 0.2,
  });

  const SentryHub = new Hub(client);

• Use hub to send errors

SentryHub.captureException(error)

Expected Result

• Should send the errors to the specified project => this works
• Should report deploys if tracking deploys is setup => this works
• Should send Crash Free Sessions, Apdex and Releases information => Not sent
• Should send performance metrics => Not sent

Actual Result

• Performance metrics not sent
• Release Health metrics not sent