In short, they completely miss the point.
See, the problem with sub ilvl 63 legendaries isn't that they are sub ilvl 63. It's that the ilvl 63 legendaries get affixes specific to them that make them good and the lower level items do not have these. Them being ilvl 63 is coincidental.
And so when you find a Hellrack, you are not disappointed because it is a Hellrack. You are disappointed because a Hellrack cannot have two sockets and a Manticore can, ensuring that a Hellrack cannot do competitive DPS. Making Hellrack spawn with ilvl 63 affixes (which it's already been able to do for months) doesn't change a thing.
Now a Buriza with ilvl 63 affixes is mildly interesting, but then a Buriza cannot do competitive DPS either and couldn't even with max level affixes both because it cannot have 2 sockets and crit damage either, and because cold damage is only 1/2th-2/3rds as high as the other elements, so no one not named Lyndon wants to use one.
It isn't just crossbows. Mempo's is used for the attack speed + solid mods combined with a random crit chance. Lacuni's is used for the attack and movement speed. Ice Climbers is used for the stat stacking + socket for more stat stacking. These items could be ilvl 58 (but still get 63 affixes) and they wouldn't be any less used so why Blizzard thinks doing the reverse would help when the problem isn't that their stats are too low, it's that they have the wrong stats is beyond me.
Sure, there are a few items that genuinely would benefit. Leoric's is used solely for the XP boost. Getting level appropriate affixes with it is a pure bonus.
But if you go and make every legendary in the game capable of dropping in Inferno with Inferno mods the result isn't that you have more drops to get excited about... it's that you have more junk on the ground, the exact opposite of the stated design goal.
In order to put more good items on the ground you have to realize what items are good and why... it does not seem they have done this yet.
They then go on to talk about adding new affixes to mods to try and make more things desirable than standard trifecta spamming but really, for every one Thing of the Deep there are ten Schaffer's Hammers and if they haven't worked out the problem with most legendaries isn't "too low numbers" but rather "wrong numbers" I expect about twenty more.
They then go into rares and such, but really there's nothing for the better here and a fair bit for the worse. See, in order to improve items they have to actually be improved.
If you have 100 items and they go 1, 2, 3... 98, 99, 100 to a given stat and then you remove 75 of them so it goes 76, 77, 78... 98, 99, 100 you still get the same number of good items. You don't get spammed with junk, but the junk at least is vendorable or salvagable. In order for item quality to actually improve the 25 items that remain would have to be crammed into less than the top 25 percentiles. That and you'd have to know what constitutes a good item, so stuff that wasn't worth picking up before because legendary or set x always outclasses it etc will still not be worth picking up.
It's still early, so they could still realize they're doing it wrong and changing it but after letting error 31048 persist for weeks - a game breaking bug by their own design my faith in them is at an all time low.