That is an insult to PostgreSQL. PostgreSQL was fully featured relational database even before it implemented SQL. It started much earlier tha MySQL.
And MySQL didn't have proper transactions or data integrity constraints (including foreign keys) for long time, while calling itself an 'SQL database'.
When JIRA practically stopped supporting self-hosted installations we migrated to YouTrack and it worked quite well. Not as powerful, but the simplicity also comes as an advantage.