I have holes on my Konas that are off to one side on the bridges, I had the same fear but it was just a bit of surface rust. On one that was resprayed this was confirmed when stripped down.
Finally made a bit of progress rebuilding after much cleaning, replacing missing ball bearings and sourcing replacement bits.
Broken/missing brifters are now correct XT thumbies and DX levers. Chopped now O beam is a slightly later and slightly rough but full length Kona one and bars are later...
I had one that was so tight the splayed thing ended up cutting out the centre and bearing whilst leaving the outer in place, fortunately the other side came out fine so reverted to a brass drift, either way you’ll need a big rubber mallet and some anger 💪
Can’t quite work this one out, kind of right but clearly tweaked
https://www.ebay.co.uk/itm/166447139066?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=aw3bB6-tS3e&sssrc=4429486&ssuid=0r6dgvlatvi&var=&widget_ver=artemis&media=COPY
Some bits do suggest that like the cassette - to get that built up with nastiness. Many of the bolts are tricky to get Allen keys in without a mallet due to crustiness. It’s going to be much slower than yours!
Front hub was brown inside with missing bearings and could undo by hand, maybe due to...