The short answer to your question is you are probably seeing an incorrect application of RDA instructions assuming the publisher's name appears on the title page.
In original RDA, there is a preferred order of sources listed at 2.8.4.2 Sources of information. The order of preference is a) the same source as the title proper; b) another source within the manifestation itself; c) one of the other sources specified at 2.2.4.
In official RDA, the element is called name of publisher and the instructions are rather vague. There is a CONDITON "Two or more values for this element appear in the source of information" with two condition options: 1) Record the value that appears first and 2) Record one or more values separately in the order indicated by the sequence, layout, or typography of the source of information. This could be interpreted to apply to names of different publishers, e.g, "Louisiana State University Press" and "Routledge" or different names of the same publisher, e.g., "Louisiana State University Press" and "LSU Press." What constitutes "first" is also vague--first on the same source of information within the resource or the first one you see in the resource?
If you were transcribing a manifestation publication statement, that might come from a different source of information than if taking the name of publisher alone. However, I doubt you are seeing that in copy cataloging.
Kate
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Kate James (she/her/hers)
OCLC · Program Coordinator- Metadata Engagement, Global Product Management
6565 Kilgour Place, Dublin, Ohio, 43017 United States
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