Yes, I like the Haynes manual too, but they aren't always correct on such things.
In the case of the ATF recommendation, the manual may be wrong, but also it was written before ATF additives changed so much in the last few years. I've run motor oil in my 240D manual transmission for about 380,000 miles or so. The transmission is still perfect, so I don't think it will hurt it.
Additionally, use power steering fluid from the auto parts store in the power steering. If you don't trust it from the parts store for some reason, get it at the dealer. But don't use ATF unless you can find type A. The additives will ruin the pump shaft seal, been there, done that.
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in