I just checked that this bug also affects version 5.1.0.
Error message is now:
org.hibernate.tool.schema.spi.SchemaManagementException: Schema-validation: wrong column type encountered in column [name] in table [SOME_ENTITY]; found [varchar (Types#VARCHAR)], but expecting [longvarchar (Types#LONGVARCHAR)]
at org.hibernate.tool.schema.internal.SchemaValidatorImpl.validateColumnType(SchemaValidatorImpl.java:170)
at org.hibernate.tool.schema.internal.SchemaValidatorImpl.validateTable(SchemaValidatorImpl.java:155)
at org.hibernate.tool.schema.internal.SchemaValidatorImpl.performValidation(SchemaValidatorImpl.java:100)
at org.hibernate.tool.schema.internal.SchemaValidatorImpl.doValidation(SchemaValidatorImpl.java:67)
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:184)
at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:64)
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:458)
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:465)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:708)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:724)
at org.nuiton.hhh9693.H2ValidationTest.testValidateHibernateH2Dialect(H2ValidationTest.java:42)