I too encountered the same issue.
I'm using a Spring Boot starter for which UUIDs were automatically mapped properly for PostgreSQL, MySQL and H2.

When I wanted to add GeoLoc functions, I added MySQL5InnoDBSpatialDialect for MySQL, GeoDBDialect for H2GIS and PostgisDialect for Postgis. UUIDs are still properly mapped for MySQL and H2GIS. Only PostgisDialect generate this issue.

I might have to stop using Postgre for now... would love to see it fixed.