Military flight files "ICE 1" civilian flightplan

In searching for Icelandair flights, I came across the following, which is supposed to be ICE 1:

flightaware.com/live/flight/ICE1

However, it was actually an A-10 making a brief trek around Davis-Monthan AFB.

Why would a Warthog have filed a civilian flightplan as “ICE 1”?

Some speculation can be found here.

We’ve seen hundreds of unique idents for military aircraft (mostly F15/F18/C17, but also A10/F117/F16). Most use the prefixes AM, CAM, ICE, RMN, or TEX and each ident typically only has a handful of flights.