1. Good to know. Let's wait and see if they fix it.
2. You're missing the "some slots" part, i.e. items that everyone can wear, as you have many more players rolling on it.
As far as I understand, in personal loot, you first roll (invisibly) if you get an item or not, and then roll which one you get. Maybe that's not the case, which would change the calculation.
Let's say (very simple example for personal loot) items for 4 people drop, one of each armor class. The boss can drop one item for every armor class, and a neck. Now you have a 50% chance for each armor item, but 4 50% chances for a neck on the entire raid. So overall, seen on the entire raid, you'll have more necks dropping on average. In the current system, 4 items would drop, with a 20% chance for every type of armor and 20% for the neck. That's where the difference on some slots comes from.
Of course, that's napkin math, presuming they don't adjust the chances for items to drop correspondingly (which we already discussed before, anyway). In an organized group, you should be able to shuffle around gear as is needed, and as other people get the item, sooner or later also the last people will get it. In LFR, every week you'll roll against 24 different people. Even if, by chance, you come up with the same ones, chances are they already sold it (because they didn't need it in the first place, which a lot of the discussion around the system is based on) and will roll again on it, keeping your chances to get it constantly low.
As for loot balance: Why not both? Why not just allow the choice of loot system that raiders requested for organized group content, without touching it in LFR - as I argued in my first post in this thread?
As seen in the discussion in this thread and in the official forums, the change to group loot in LFR seems to also cause a lot of friction within the community. If they already considered all I wrote before and baked that into the drop chances in LFR, why not just keep the rolls in the background to avoid this friction?