Yup! See https://jepsen.io/analyses/mysql-8.0.34#list-append, which also has a link to the code: https://github.com/jepsen-io/mysql/blob/4c239cb5c66a7f1a55fa...

This isn't CONCAT-specific, BTW--we just use CONCAT because it allows us to infer anomalies in linear, rather than exponential time. Same kinds of behaviors manifest with plain old read/write registers.