Wow...I knew I shouldn't have tried to help by clarifying that "platform" mistake. Some folks on this board make posting as fraught as boards on politics, religion, or oil changes.However, let's be objective; JMHO, but I can't find any content in the Mini which might be considered "much more premium" than the Bolt; examples, please. Again, being objective, I find after a side-by-side comparison the i3 has much higher quality of material, fit, finish and content than the Mini. As to "weird", some of us are all in favor of it.
Other than that, I simply replied to your subjective post "Why not just buy a used i3; one with much higher content and trim than the Mini would seem to have", which indicates you have no experience with a current Mini, with my own opinion based on experience with all three vehicles in question. Again, so much for trying to help the OP. And I have no idea why what I may or may not think of as "sporty" has anything to do with the post you quoted.
As far as "my money, my car, my decision" go I obviously chose a Bolt as it best fits my needs. I shopped the i3 but they don't work for me for much the same reason the Mini SE does not. If electric range was higher I would choose either BMW product. As I said before they are both just nicer places to spend time, subjectively of course.
Bolt vs Mini examples? The seat construction & materials and the dash/trim/other interior bits really make the Bolt pale in comparison. The narrow Bolt seats & the hard armrests can make comfort a challenge whereas the Mini is available with those fantastic BMW sport seats. That's an opinion btw.