Lead oxides can be fuzzy, and white and they can be gray and can be black. Oxide dose not gust mean has Oxygen at the end its that some thing with a negative charge gust stuck it self on some other molecule most of the time this other thing has a slight positive charge. (not really a good definition but its easy)

Dead boring from hear down to most all the people I know.

It dose not realy matter, the battery gust sitting will go "bad". Its the battery it self, its a oxidation/reduction reaction that makes the power in the first place. Add to that that half the lead plates are a lead oxide even when the batter is new.

A cell in the battery looks kinda like this (Pb)|(PbO2) this alows hydrogen ions (H+) to pass around the plates moving electrons making power (and others things but lets not make it hard)
lead being shone as (PB) lead oxide shone as (PbO2) and | is the acid (H2SO4) and space between.
The problem comes when the battery gets old no charge. The cell gets to look like. (PbOxidesonething)\(PbO2) (or PbSO4\PbSO4and PbO2) the \ being lead sulfate and water (PbSO4) and H2O with little H2SO4 so few H+ ions. So the lead can oxide on the out side (of the lead plate) to lead sulfate PbSO4 or lead oxide PbO2

Flushing out the battery will remove the water and some of the lead sulfate, adding new sulfuric acid adds in more H+ ions but dose not mean that the plates will have enof (PB), lead with no oxides on the end.

Some light reading. From Wiky not grate but longer hehe
Sulfuric acid - Wikipedia, the free encyclopedia

Lead-acid battery - Wikipedia, the free encyclopedia

To put in other words its a bottle of Coke its been open and left in the sun for a year. You can dump out the bugs put more Fuzz but its still not a good a fresh cold Coke.