View source for URL fields

For Limesurvey 2.x the 'PASSTHU' notation doesn't seem to work, but just putting the field reference in direct (after the '=') does work.

For for example adding "?myvar={PASSTHRU:myparam}" doesn't work and yet "?myvar={myfield}" (where myparam is linked to myfield) does work. 

This would suggest that the "URL parameters" might be not only not working, but redundant.