However it's not transparent at all. If any problem arises (and I mean non-intentional problems due to miscommunication, not necessarily a scam attempt) then the escrow (who is an alt of the other party) can't act neutral, he just can't. If the 2 persons who are dealing forget to agree what to do on an specific circumstance each of them may think differently; I've seen cases when they assume completely different things as obvious. A neutral third party could solve this but in this case there's no third party to do it.
You are correct, there are possibilities to have miscommunication issues. This is a risk that is being taken when escrowing your own deals. However this possibility of this happening is the same as if there is a direct trade between two parties.
If you and I are trading, and you are selling 1 BTC for 240 dollars, then what is the difference between you sending me 1
BTC, and me sending you CAD$240 from QS, verses me sending you CAD$240 from an alt? Even if the fact that what currency is being used is not documented properly (an escrow agreement should do this), it is still a scam in both instances. If this would be done as a direct trade, then it would be possible to weasel your way out of it, however if you were acting as an escrow, then your reputation as an escrow would be damaged because you did not properly gather all of the facts prior to advising that it is safe to send money