I usually have junior staff "file" the extensions at my company (though this year I'm doing it). I run the computations, create a list of who needs what, the junior fills in the forms, I review and make sure all forms are correct, the junior writes the cover letters, I review and make sure (a) all extensions that need doing have been done and (b) all the extensions are on the cover letter.
It's fairly standard business practice. The computation is usually done by someone knowledgeable, but the dinky little forms and the cover letters are done in batches. It's how the juniors become seniors, by being given "easy" work and proving their mettle.
Another fairly common business practice is to hire in extra help during the busy season. This may be what your accountant has done.