The problem is we don't infer the indent width for case indents in adaptive formatting. We see that the case indented, but don't record the indent.
When you select an expansion like that, it's getting sent to the beautifier to take care of the formatting, and the beautifier has to go strictly by what's in the beautifier profile. The "picking the indent from elsewhere in the switch" is an editing heuristic, and not usable by the beautifier. Adaptive formatting tweaks buffer profile settings to match what's going on in the file, but doesn't set this particular setting.
So I'll need to add case indent width as a value we can infer. I'll fold that into the other adaptive formatting changes I'm doing for the point release.
The only workaround is to disable the beautification of codehelp expansions like that by going to Documents -> C/C++ Options -> Editing, and under the "Beautify" group, uncheck "Beautify alias expansions".