Is this based on recent experience? I recall adding my number to multiple reservations as recently as September via the Bonvoy app.
The number should still appear in the email confirmation from II under the Unit Details. There were issues when II first changed over to the new email confirmations where the Marriott confirmation number wasn't appearing in the email. I understand that they have fixed the issue. If the Reservation Number isn't in the email, you can contact II and ask them for it. I have had issues adding the Bonvoy number on the website as it seems to produce an error message when looking up the reservation. I find it much easier to add via the Bonvoy mobile app.
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