I combined the SPG account (very little activity) to my Marriott account about a month ago. Was rather perplexed to see that my upcoming Westin reservation doesn't show up when I logon to Marriott.com; yet I received an email today that confirms the reservation. I thought that when you combined the accounts, you would only have the one (Marriott) account. Another example of "seamed" (vs seamless) integration?
Yes, others have reported similar experiences after combining their accounts, but after some time they've been rectified for many.