This does seem strange, Matthew. All I can think is that there must be a timing issue somewhere, and at the point SiteCatalyst is firing, the data is not yet available. Since this is quite a specific case, please get in touch with your account manager for assistance, or send me a private message with the link to your test site so that I can verify why this is happening.
Craig.
Check out our new Swift integration library for iOS, macOS, tvOS and watchOS: https://github.com/Tealium/tealium-swift with updated
documentation https://community.tealiumiq.com/t5/Swift/tkb-p/swift.