You can't say that even GW doesn't charge people for errata and then completely ignore the fact that WH40K 6th edition came out a couple months before X-Wing's original release, and 7th edition came out before X-Wing's Wave 4...
And, technically, FFG doesn't charge for errata. Errata are all in the free, PDF version of the FAQ.
I think you're looking for the word "formally" rather than "technically" here. As I said, ceteris paribus there is no reason to omit Chardaan Refit; nobody is going to field the basic A-Wings without upgrades anymore, so it's as good as an erratum ("if your A-Wing has no missiles, subtract 2 from the points cost"). "Technically" it's an erratum, if you wish.
Looking at how it works out in practice, a single card would have been okay as far as I am concerned. Now, I suppose that three copies of the card is useful to tournament players. I'd prefer it if the game was aimed at those who play just for fun and less for organized formal competition.
Perhaps it is to make up for the expenses inolved in making that ubercompetitive Fat Han that is so popular at tournaments.