Both the AWS Data Catalog table AND individual partitions have a serialization setting. An update to the serialization lib settings on the AWS Data Catalog table do not automatically update the serialization settings for the partitions on that table.

You can check the serialization lib on the partitions by Viewing the Properties of an individual partition on the table in the AWS Data Catalog console.

It may be necessary to add a Classifier on the Crawler that creates the table, or to recreate the partitions after updating the AWS Data Catalog table.

The bottom of the docs on this page have additional details on adding a classifier and how LazySimpleSerDe will be selected by default unless a classifier is added that specifies OpenCSVSerDe: docs.aws.amazon.com/glue/latest/dg/add-classifier.html