Chrysler: LH cars Power Steering Fluid

While wondering what is wrong with my 99 Intrepid steering
(it squeaks loudly while making turns, especially to the
left) I noticed this strange factoid:

The 1999 LH service manual says, "use only Mopar Power
Steering Fluid, or an equivalent. DO NOT USE AN TYPE OF
AUTOMATIC TRANSMISSION FLUID."

The 2002 LH service manual says, "Use only Mopar ATF+4
Automatic Transmission Fluid in this power steering system."

Any ideas why the change from use no tranny fluid to use
only tranny fluid? I thought maybe it is because the ATF+4
is newer. But the 1999 service manual does make references
to ATF+4 (9602) because it was used in the 1999
transmissions. (Although they do slip up in a few places and
call for ATF+3 fluid, which was cleared up by a service
bulletin).

My fluid was changed over the summer, and the receipt says
that factory part number 4883077 (OIL POWER 1081033) and
also factory part number 6504014 (RETAINER).

Was this the right fluid for my car? Also what is the
"RETAINER"?