I don't get it. The proper length and style for resumes is totally industry specific. It can vary widely between industries. For some jobs, a 2+ resume is a no-no, but in others they want the detail. You shouldn't say the practice is for a 1 or 2 page resume, unless you also state the field you work in.
My guess your ad is drawing interest from people that work in the federal sector that are used to making large federal-style resumes and just don't know that isn't the practice in your field.
You should look closely, as the first page might be a summary page that replicates a traditional 1 page resume and then has more detail in further pages. So there is no harm if you just look at the first page.