CYYJ
Michael
The UK has what is called a "saline atmosphere" - it's surrounded by salt water, winter temperatures are mild, and humidity is high. That, plus a longer riding season in parts of the UK (leading to riding the bike when roads have been salted) is why rotting swingarms are common in the UK....The rotting of the swingarm really isn’t a thing here in the US (mostly in the UK) ... I assume more salt spray in the air, etc. in the UK...
The problem is not limited to ST 1100 swingarms. I have seen the same problem with aircraft operated in UK coastal areas, and automobiles in the UK.
In other words, it's a regional thing caused by the nature of the climate.
Michael