App-V can't handle application with backslashes in FileTypeAssociation ProgId

Question

I've been working on sequencing an application which writes something like this to HKLM\SOFTWARE\Classes (actual vendor & product names changed):
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.someextension]
@="VendorName.Ext\Foo\Bar"
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\VendorName.Ext\Foo\Bar]
@="The App Name Shortcut"
"InfoTip"="blah blah blah"
"NeverShowExt"="-1"
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\VendorName.Ext\Foo\Bar\shellex]
When I try to sequence this, the sequencer tells me "Invalid manifest detected". When I add this package to a client, the debug logs show:
2015-Feb-12 11:52:45.699 - Manifest: [1792].[4448]: ERROR: ManifestUtilities::ValidateDocument() - A manifest document failed validation against the schema(s).
DOM Error: -1072897687
Reason: 'VendorName.Ext\Foo\Bar' violates pattern constraint of '[^\\]*'.
The element '{http://schemas.microsoft.com/appv/2014/manifest}ProgId' with value 'VendorName.Ext\Foo\Bar' failed to parse.
AppxManifest.xml contains:
<appv:Extensions>
<appv:Extension Category="AppV.FileTypeAssociation">
<appv:FileTypeAssociation>
<appv:FileExtension>
<appv:Name>.someextension</appv:Name>
<appv:ProgId>VendorName.Ext\Foo\Bar</appv:ProgId>
</appv:FileExtension>
</appv:FileTypeAssociation>
</appv:Extension>
I worked around this by moving VendorName.Ext\Foo\Bar to a new location where .someextension didn't need slashes to refer to it, but I'm wondering whom I should send a bug report to. Should
the vendor not be writing this value, or should App-V be handling these backslashes?

Answer 1

The application is
The Raiser's Edge 7.93. The install & update process is ugly (unless users are all administrators), so I've been experimenting with wrapping it in an App-V container.
Are you aware of any Microsoft documentation I can point them at to back this up?