It seems like you already found a previous forum post about this. I’ll link it here for the benefit of others:
Since that post, we’ve finished the update to Date&Time fields in KNIME, but Tableau made some significant changes on their end to the way it handles imported files in version 10.5. I can tell you we’re actively working on our Tableau integration, but for now, KNIME is still exporting dates as strings to Tableau.