The --sampler option doesn't make it a debug swf - the ActionScript sampler has a slightly higher overhead on iOS than for other platforms (you shouldn't leave it on when you deploy your app), but it's not as high an overhead as being a debug swf.
As far as I'm aware, Flash Player/AIR will only tell Scout that it's a debug swf if it encounters the EnableDebugger swf tag. It's possible that the latest version of AIR is reporting this incorrectly, but I'd double check to be on the safe side (you can use SWFInvestigator to take a look inside your swf). If you're sure that you packaged your IPA correctly, then I wouldn't worry about this message.
It might also be something in the way you packaged your IPA. If you used the ADL tool to make your IPA via command-line, you might have used a package type that makes your release a "debug" application. I would check if you have "-target ipa-debug" switch in your command line, for example, because i think that package type will be considered a "debug" version.
To make a "release" IPA for local testing, use the "-target ipa-ad-hoc" or "-target ipa-test" switches
I have this same problem, Scout tells me my swf type is debug, although my compiler has "-target ipa-ad-hoc" parameter.