We disagree with your commentary. Where do you get the wrong idea that "Apple will end macOS version updates for the M1 Studio in ~3 years"? My 2016 MBP has been getting all OS versions for more than 7 years, up until Ventura, 10/2022. And AFAIK Monterey (I am now on 12.6.3) still gets security updates when necessary, even though I cannot move to Ventura.The 7,1 will remain useful much longer than an M1 Studio, even if it can't run a current macOS release. Apple will end macOS version updates for the M1 Studio in ~3 years after it's discontinued and there won't be anything you can do with it besides accept the security risks of using an old macOS version. The 7,1 will even remain useful longer than the upcoming M2 Ultra Mac Pro, which is already obsolete since M3 is almost here.
We do agree that the 2019 MP was a good, versatile desktop. However in my experience even the good, versatile desktops age out at some point for app/OS software or hardware reasons, including hardware failure. The tech world keeps advancing. Best planning policy IMO is to allow for about ~6 year life of a box.