The SimplifyCoefficients(S, funct) calling sequence applies the funct function, where funct is not collect, to the coefficients of the series  (both particular and general coefficients).

The SimplifyCoefficients(S, collect, collect_expr, other_args) function applies the collect function to the coefficients of the series S (both particular and general coefficients). The user must specify the expression(s) to be collected by collect_expr. The user can specify a function to be applied to the collected expressions by other_args.