I recently used my $300 Marriott eGift Card which I received with the Marriott Bonvoy Boundless credit card.

Upon checkout at the Westin Phoenix Downtown, I had to forward my gift card email to the supervisor. She said that I should expect an email in about an hour, but I didn't receive confirmation that my gift card was applied to my bill until about a month later.
It took almost a month for the gift card to be applied to my bill..