Extra nuts are larger and just used as spacers, doubt it is your issue, but I would say poor from an engineering point of view.
Back to the front spring eye, all that rust suggests to me something is moving in there.
I see slack and loose u-bolts all the time at work, before I even start hitting things it is the fresh rust that is the giveaway sign, more of an issue on the toy trucks rather than the full size ones.
I tried polybushes once on my 90, it was never right aftewards, several months later and back to std metalastic bushes and normal service was resumed, this bought about a big downside to the polys, they let water in lots of it, and this helps the bolts/sleeve rust badly making things a right barsteward to get apart.
Do not see polys on commercial vehicles, says it all for me.
This is the front lower arm off a D3 that had polys fitted, they do not do well on polys!