The Hill does a comparative study of FOIA logs from Federal agencies. They sent 70 requests for logs to 70 agencies, and waited (and waited) to compile the results.
Some executive agencies sent FOIA logs with the requesters’ names, but without their affiliations. Other logs were handwritten. A few agencies complied with The Hill’s request in days, but most took months.
I'm never surprised with the results of media audits of FOIA where lots of requests get generated in a short amount of time to a lot of agencies. You're bound to find some variation, and since you're sending what is essentially a form letter to some clerk who you don't know, it's likely to go at the bottom of whatever queue forms to do the work.