Those are special parameters, which are only used in the pattern editor to set the L/R delay times to the current “L/R sync Time” values. They basically do what hitting the “Set” button in the delay GUI does. So both is expected.
Emphasis added. I would have expected writing to these parameters to only change the delay time when line sync is enabled. I’m not in front of Renoise at the moment, but I think it is the other way around (only works when line sync is disabled).