data stack in INLA step

[timcdlucas]

stk <- inla.stack(data = list(y = dataframe$y), 
                  A = list(A, 1),
                  effects = list(s.index,
                                 list(y.intercept = rep(1, length(dataframe$y)),
                                      covariate = dataframe[-1])), 
                  tag='est')
                  
stk <- inla.stack(data = list(y = dataframe$y),
                  A = list(A, 1), 
                  effects = list(c(s.index, list(y.intercept = 1)),
                                 list(dataframe[-1])),
                  tag='est')

I think both of these formats work in inla but only the second seems to work in INLAstep. No idea why.