Agreed, I think the authors of this study oversold the conclusions. They have a valid point insofar as delegation is not a magic bullet, and people often over-delegate.
Perhaps that latter is because they are OK with representative democracy in principle, but want the capacity to revoke & reallocate their vote without waiting months or years for an election.
I found the study disappointingly shallow and conclusory by comparison to the usually excellent standards of the NBER, but it might be that the cost of surveying people limited the depth of their investigation.