I got the same issue and I think I found the solution.When using the contact endpoint (https://api.qualtrics.com/reference#create-recipient-contact) it seems that the embeddedData values only accept strings.Changing {"id": 1} to {"id": "1"} in my embeddedData fixed this issue. I guess that if it doesn't work well for integers, it could be the same for booleans. In your case quoting the "false" might do the trick.However, in the contact import endpoint (https://api.qualtrics.com/reference#create-contacts-import) everything works fine for me without adding quotes.
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