Mark Racco did 3 videos back then - Mr. Brownstone, My Michelle, and performance version of You Could Be Mine (that means there are two versions of YCBM video - the performance version was first and then they made the second one for the T2 movie alternating performance footage with movie footage).
as for Mr.B and MM specifically chosen - maybe it was just because UYI weren't quite ready to go yet, so they went back in their catalog before they felt that the UYI material is finished. note that UYI vids were made quite with delays and sometime it took years until a vid was made - for example Estranged music vid was only released in December 93.

yes, sort of we do have big part of that! count with me:

Catcher In The Rye
I.R.S.
There Was A Time
Atlas Shrugged
Perhaps
State of Grace
Prostitute
The Blues
Madagascar
Chinese Democracy
Rhiad & The Bedouins
Silkworms
likely also Nothing
likely also Hardschool
maybe also Eye on You

+ instrumentals:
Oklahoma
Quick Song
Zodiac
D-Tune
Curly Shuffle
maybe also Mustache
maybe also P.R.L.
maybe also Thyme

yup. the title track's intro on the album is just ridiculous and idiotic. the original intro on those discs makes me huge googsebumps every time I start listening to it. wtf were they thinking?

to make the confusion absolutely clear and to answer the OP's question:
1) a leaker or leakers leaked these songs.
2) so they were leaked.
if the leaker is smart, nobody will know who he or she or they is or are.