It's possible we are caught between terminology of geographic areas. I might need to ascertain if this board is US-based or UK-based so as to acknowledge differences and may need to tailor my responses.
In that case, I can't be sure what you mean by "scarify." To me, scarifying the soil is scratching the surface, so please correct me if you meant something different.
Aerating with hollow tines means you remove plugs of soil. Am I right? To do it properly, you will remove plugs roughly 3 inches deep and roughly 3 inches apart. Leave the plugs where they lay, and they will mulch themselves back into the soil. The process negates the need and purpose of scarifying because it ruins whatever you did previously and essentially creates a somewhat new surface of soil/grass. So, your earlier efforts are wasted and secondary to a superior process. When it comes to mechanical processes, like aerating, scarifying, power raking, etc., you want to decide on the side of optimum benefit. If thatch is a problem, for example, aerating solves that problem also by breaking up the thatch layer, meaning there would be no need to both dethatch and aerate.
In addition to making the soil friable for penetration of air, moisture, and nutrients, as well as improving drainage, aerating is especially beneficial when seeding because the plugs carry the seeds with them as they mulch themselves into the soil, which optimizes seed/soil contact.