Check whether the Test Sequence block in the sltestRollRefTestExample model uses scenarios. In this case, the block has not been set to use scenarios, so isUsingScenarios returns false.

Model = 'sltestRollRefTestExample';
load_system(Model);

use_scen = sltest.testsequence.isUsingScenarios...
   ('sltestRollRefTestExample/Test Sequence')

use_scen =

  logical

   1
 

close_system(Model,0)