The retcon was not about the Reapers. the retcon was about how many ships were lost in the battle with the Sovereign and the geth fleet. Sure it is never truly stated how many ships of each council species were lost in the battle but why would then shepard remember only the eight cruisers and no other ships? then say that Turians lost 20 cruisers? That doesnt seem to translate to the third of fleet lost for 3 different fleets. And Joker says that the fifth fleet is ready for action, he didnt say any other ones are. It is a debatable issue of who and how many ships were lost but if the power level of the reaper was one Reaper vs one fleet( three thirds make one) then the war could have been easily won with a few dozen reapers, maybe a hundred. Not the horde of them that we see.
I wasn't very accurate there -- what I meant to ask was what the significance of the retcon was.
Let's say the WA stats were set where you think they ought to be; instead of the fourth-largest fleet in the galaxy losing 1/5 of its total strength, it would have lost only a small fraction of that strength. What would change?
Nothing. This would change exactly nothing about the military situation. The Reapers would still have overwhelming superiority.