It's like saying (hypothetical time)
"Any family member may attend your ceremony and he/she will be seated near your place in the line."
Would you assume from reading this that you can invite ALL your family to the ceremony? It's the same sentence structure and uses the same words.
Would you assume you are only allowed to invite one family member?
One thing no one seems to be mentioning:
"Healing Guides (11th level): When you restore
hit points with your healing spirit power, any ally
adjacent to or within a conjuration or a zone that you
created with a shaman power or a shaman paragon
path power
also regains hit points as if he or she were
adjacent to your spirit companion."
The word also is in there. They don't just regain hit points as if they were adjacent, they ALSO regain hit points as if they were adjacent.
Another thing. Yes, they could have said "all allies ...", but then again they could have said "any one ally ..." Then again, because this only applies to some allies (the ones that are in the right places), all allies may have been considered confusing for some (does it have to be all or nothing, what happens if there is only one ally, etc).