One issue with this argument is that there are very few engineers that have had the opportunity to design satellites that are; this large, are designed for mass manufacturing, rapid iteration, failure allowance, and with access to a reusable launch vehicle with the capability of Starship (where it's also unknown what launch mass capability they will end up reaching).
The satellites built by SpaceX so far, and their engines, are quite unlike most previous space engineering due to these reasons. Given the undeniable success they've had in building Starlink, with each version growing considerable in size, I just don't see which engineers would be able to fully rule out the math that SpaceX might be working on here, exactly because there are so many parts of the total equation and where SpaceX are moving outside the previous design envelopes in many dimensions.
Of course I'm personally not convinced or able to know whether this is economically sensible - I just believe it's very difficult to fully rule out given the track record of SpaceX - and given that there doesn't appear to be any singular insurmountable thing that needs to be figured out here. Hence why I said in my original post that this is why I'm excited to see the design space explored.