66 Dart GT HT Whatsitgonnabe?
Does the use of stainless fasteners with aluminum reduce those problems?
I couldn't say, I'm not a chemist. The problem is the same on our '99 Audi but I've managed to loosen both sides with relative ease, compared to this one, so I think the problem is worse on the newer model. Maybe different coating on the hardware, maybe different composition of the casting.
The spindle is marked AlSi7Mg. I suspect that means it has a 7% silicon content. I have experience with silicon-alloyed aluminum materials from my past career and it makes aluminum very stable. Mercedes uses silicon-alloyed aluminum cylinder sleeves, i think the silicon content is upwards of 30% in those.
I don't know how this affects the chemistry between the casting and the bolts but I'm sure the Audi engineers try to make this work.
I had a similar problem when I removed the rear sway bar bolt trying to get the coil spring back in place last summer. The thread stuck to the bolt so I ruined the threads backing the bolt out and had to put a thread insert in.