I'm not claiming this is a good idea today, nor claiming Starship looks to hit its cost goals any time soon, but I would note that COTS hardware works fine in LEO. SpaceX's Dragon is all COTS, using radiation tolerance rather than hardening.
True. But this relies a lot on software and probably some specialized details in hardware as well
Your Dragon docking maneuvering requires way less calculations than your typical AI training. Hence it is ok to have HW do the same calculation multiple times and check the values.
This is different from AI training where you want the most reliability 24h/day
Another aspect that is entirely missing from that pdf that doesn't necessarily convince me these people have a plan.