in this case, i think reporters are basiclly using words "proprietary" and "restricted" interchangeably.
right now, AAC from iTunes only plays on iPod. WMA plays on any mp3 player with WMA support. so even though AAC is "open" (fairplay, of course, is not), it's "restricted." WMA really is "proprietary" but since it's not really "restricted," the fact it isn't open is not a trouble for most consumers.
in stricter sense, gif format is also proprietary. but for most users, usage of gif is unrestricted, so it's not a big deal. (the program users uses for gif manipulation, of course, included the licensing fee...)
ignorant, yes. is there some kind of conspiracy to try to stick (unjustified) evil "proprietary" label on iTMS?, no.