This is the Lippert sheet regarding the use of fluids in their system.
https://cglapps.chevron.com/sdspds/P...&docFormat=PDF It says automatic transmission fluid, but it also says hydraulic fluid with a pour point lower than -44 degrees F.
This is a chart from Chevron about their hydraulic fluids,
https://cglapps.chevron.com/sdspds/P...&docFormat=PDF
and it only shows their AW32 with a pour point of -13 degrees F.
I converted my system over to ATF early on and have had no issues with it, so use what works for you. I've never thought to question the use of AW32, but I guess it works. My understanding is, ATF is hydraulic fluid with additives and dye, so either should be fine, except I can buy ATF in quart sizes which is easier to handle.