You can put <meta> tags directly into the configuration file as macros, and not have them in your FrameMaker document at all. See §18.5.2 Assigning code to [Inserts] keywords for splits and extracts and §28.1 Defining and invoking macros.
13.4.6.2 Providing meta content with FrameMaker markers
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13.4.7 Specifying nonstandard values for declarations