The question isn't the default but rather the ability to opt out. And no, "drop XML on your ISO image" is not an acceptable bar for that.

But, more importantly, it's not a given that this will continue working onwards. As things are, there have already been three different ways to force the installer into letting you use a local account, the most recent one of which involved using the recovery terminal when booted from ISO - that's already way past most users. And yet Microsoft methodically killed each and every method every time, so I fully expect your suggested workaround to stop working. They seem to be very determined to ensure that no "non-enterprise" version of Windows lets people do that.

what do you reckon it costs microsoft to support people that "opted out"? what amount of legal boilerplate would indemnify Microsoft against lawsuits over lost data because someone chose to opt out?

If the only option is to modify the installer the only people who are going to opt out are the sort of people that understand that microsoft has no responsibility to our data, and pretending they do is silly. It's pure CYA from Microsoft.

If you personally don't like it, then use their automated thumb-drive creation tool (at that same link) to make a new bootable USB stick that installs with the "opt out". I modified the ISO because i was installing on a Virtual Machine. If i was gunna do it on metal i'd use a USB stick because all my optical drives are USB and not that fast.

I don't think we disagree, i think we're coming at this from different sides. I don't expect microsoft to spend more money than they have to.

I need to remind here that the very notion of a cloud account didn't exist for literally decades in the past, and I don't recall anyone suing Microsoft about losing a password etc. The legal angle for such things is firmly covered by EULAs, anyway - I worked for Microsoft for 15 years, and I can assure you that the lawyers there are very adept at such things. And then, of course, Apple clearly doesn't have any legal issues despite only having local accounts on macOS even today. Nor are cloud accounts free of legal issues themselves, what with GDPR etc. In fact, I'm pretty sure that cloud accounts are more "legal heavy" on the whole.

I would believe that it was purely about costs if they simply removed the checkbox from the installer but still left the command line workaround - that is plenty sufficient to ensure that the user "understands that Microsoft has no responsibility", and generally to prevent the clueless from shooting themselves in the foot. But given that even such advanced techniques were removed shortly after they were discovered, I'm certain at this point that it is a concerted effort to drive all non-enterprise users towards cloud accounts. And given that Microsoft is heavily investing into ads, and generally has a Google envy for a very long time now, I think that it any product decision that clearly correlates with more ability to track users and collect their data is likely to be at least partially motivated by that, just as it is in case of Google.