HTML Email sent with a Google's Event Schema is not adding event to Google Calendar

Question

I am sending an HTML email to my costumers after they book a reservation on my restaurant's website. I wanted the email to automatically add an event to the costumer's calendar, and so I was adding the following script after the HTML opening body tag to test it (https://developers.google.com/gmail/markup/reference/restaurant-reservation):

<script type="application/ld+json">
{
  "@context": "http://schema.org",
  "@type": "FoodEstablishmentReservation",
  "reservationNumber": "OT12345",
  "reservationStatus": "http://schema.org/Confirmed",
  "underName": {
    "@type": "Person",
    "name": "John Smith"
  },
  "reservationFor": {
    "@type": "FoodEstablishment",
    "name": "Wagamama",
    "address": {
      "@type": "PostalAddress",
      "streetAddress": "1 Tavistock Street",
      "addressLocality": "London",
      "addressRegion": "Greater London",
      "postalCode": "WC2E 7PG",
      "addressCountry": "United Kingdom"
    }
  },
  "startTime": "2022-10-01T08:00:00+00:00",
  "partySize": "2"
}
</script>

But the event is not being added to the calendar...

To test this I am using gmail to send emails to myself (from [email protected] to [email protected]) (skip google authentication). And I am using the Restaurant reservation schema (suported schemas).

When I inspect the received email's HTML that script is gone. I do see it if I check the original message ("Show original" option on gmail). Is this normal? Did Google/Gmail already "took care of it" before it being displayed on the HTML, or should it be there for Google/Gmail to be able to "recognize it"? I wanted to at least understand at which step the problem is happening.

Any ideas?