PlatformImplBase.processChange(RecreateTableChange) does not migrate (autoincrement) sequences, but does call SqlBuilder.dropTables. PostgreSqlBuilder.dropTables explicitly drops the sequences:
for (int idx = 0; idx < columns.length; idx++)
(On the other hand, HsqlDbBuilder does not drop the sequence for instance.)
The sequence is created again, but that causes 'duplicate' errors on the column using the sequence.