Use pText->setAlignmentPoint(OdGePoint3d(outlineCenter.x() , outlineCenter.y(), outlineCenter.z())) and set text alignment by next way
pText->setHorizontalMode(OdDb::TextHorzMode::kTextCenter );
pText->setVerticalMode(OdDb::TextVertMode::kTextVertMid) ;
Method adjustAlignment(); is called while text entity is closed but may be called directly after append in block
m_blockTableRecordPtr->appendOdDbEntity(pText);
pText->adjustAlignment(NULL);