Most of the time, if a D1 school does not list or advertise other schools then there are probably not too many other D1's attending. Plenty of local D2, d3, NAIA's etc. will be helping out.
I was not familiar with this particular camp so I looked it up. Looks pretty good to me!
Over 25 of the country’s top academic colleges/ universities will be in attendance, including:
1 UNIVERSITY OF RICHMOND (D1, #23 in National Liberal Arts Colleges)
2 Princeton University (D1, #1 in National Universities)
3 Harvard University (D1, #2 in National Universities)
4 Brown University (D1, #14 in National Universities)
5 Georgetown University (D1, #24 in National Universities)
6 Lafayette College (D1, #39 in National Liberal Arts Colleges)
7 College of William and Mary (D1, #40 in National Universities)
8 Lehigh University (D1, #50 in National Universities)
9 Penn State University (D1, #57 in National Universities)
10 George Mason University (D1, #153 in National Universities)
11 Towson University (D1, #197 in National Universities)
12 High Point University (D1, #1 in Regional Colleges South)
13 University of Charleston (WV) (D2)
14 Swathmore College (D3, #3 in National Liberal Arts Colleges)
15 Bates College (D3, #21 in National Liberal Arts Colleges)
16 University of Rochester (D3, #29 in National Universities)
17 Franklin and Marshall College (D3, #38 in National Liberal Arts Colleges)
18 Hendrix College (D3, #92 in National Liberal Arts Colleges)
19 Randolph Macon College (D3, #111 in National Liberal Arts Colleges)
20 Babson College (D3, #1 in Entrepreneurship)
21 Roanoke College (D3, #130 in National Liberal Arts Colleges)
22 Virginia Wesleyan University (D3, #164-215 in National Liberal Arts Colleges)
23 University of Mary Washington (D3, #16 in Regional Universities South)
24 Cairn University (D3, #126 in Regional Universities North)
25 Milligan College (NAIA, #13 in Regional Universities South)