It seems like $modelConfigurations can also be of type Illuminate\Database\Eloquent\Builder and Illuminate\Database\Eloq...gHasThroughRelationship; however, parameter $arrays of array_merge() does only seem to accept array, maybe add an additional type check?
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Ignorable by Annotation
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If this is a false-positive, you can also ignore this issue in your code via the ignore-type annotation