Arguably this is also true, if you make certain allowances:
“The comprehensive review of evidence which accompanies the consultation makes it clear that a large body of academic tests and research consistently show plain packaging makes tobacco products less appealing to young people." [Sheila Duffy, ASH Scotland]If you allow for the fact there is no way to test results empirically, yes, it is easy to believe that the only way to get a study in plain packaging published is to find that it would help reduce child smoking.
But no study can show such a result as there are no empirical data. There is no plain packaging in the shops yet. Studies can only speculate. Even if they find that plain packaging reduces the appeal of tobacco in a controlled experiment, this has no bearing on what children will experience in the real world and young people have no way to predict their future wants and needs as their awareness increases in their progress to adulthood.