It doesn't appear to be of significance unless the Army placed the flags, I think the eagle is there as to be a more decorative flagpole. So if the Army placed the flag, then an eagle would be appropriate I'm sure for even former presidents.
Here's the regulation (page 119):
8–2. Flagstaff head (finial)
The flagstaff head (finial) is the decorative ornament at the top of a flagstaff. This does not restrict the display of a State flag from a staff bearing a State device when national and other State flags are displayed from adjacent flagstaffs; however, the Army does not provide such devices. Only the following finials are authorized on the flag used by Army organizations:
It doesn't appear to be of significance unless the Army placed the flags, I think the eagle is there as to be a more decorative flagpole. So if the Army placed the flag, then an eagle would be appropriate I'm sure for even former presidents.
Here's the regulation (page 119):
8–2. Flagstaff head (finial)
The flagstaff head (finial) is the decorative ornament at the top of a flagstaff. This does not restrict the display of a State flag from a staff bearing a State device when national and other State flags are displayed from adjacent flagstaffs; however, the Army does not provide such devices. Only the following finials are authorized on the flag used by Army organizations:
a. Eagle (Presidential flagstaffs) (see fig 8–1).