The boms/preview-xxx boms are importing their boms/standard-xxx analogues. That seems wrong and is kind of a leftover from the days 'legacy', when 'standard' and 'preview' used the same deps while legacy was an outlier.

Conceptually preview-xxx, like standard-xxx should depend on common-xxx.

Of course as soon as I do this we'll go back to having legacy. But I think if that happens we should model the dependencies differently, e.g. with a 'current-xxx' to hold things shared between 'standard' and 'preview'. Or something.