maybe not a big deal for you, but a big deal for anybody out there with a GFX1070...
You did just accidentally prove my point: The monitor was released around May 2017. This firmware you linked has the date Jan 19th 2018. Anyone with this scenario who bought the monitor in 2017 would have seen it doesn't work, and would have had to wait anywhere from one to six months - but these customers would not have been able to know at the time of purchase when the fix would arrive or if one would come out at all.
What these customers should have done and hopefully did was return the monitor because it was obviously defective out of the box and if Dell had decided not to address the issue at all these customers would have been left with no recourse.
Okay fine I get it, the possibility to upgrade the firmware at home does have a benefit. If you receive older stock and your monitor has an issue right out of the box that can be fixed immediately, fair enough, that's better than having to do a return.
Nor can any modern monitor.
The Studio Display already had issues as mentioned before, with brightness control and audio. It already needed fixes. I have a couple of iiyama 4k monitors I got a couple of years ago and due to work I have to hook up a variety of computers to it. There hasn't been an issue with using DisplayPort on any Windows computer nor any Mac, Intel or ASi. The basics like 120Hz just work, though there is no HDR to begin with.
I don't need USB-C to use the speakers, they are recognized via DisplayPort just the same. I can use USB-C if I want to get the charging functionality and USB hub, but if for some reason the USB-C port were incompatible with my latest Mac I can use DisplayPort and don't have a bricked monitor until the manufacturer provides a fix in one month, in six months, or perhaps never.
your 'just a DisplayPort Monitor' will still have potentially buggy firmware - if you never need an update (esp. if you buy a brand new model), lucky you.
If you say so, my experience has been that DisplayPort works. Maybe brand new models are really bad in this regard, but I don't see why that should be the case. I have certainly seen issues where on some Mac you couldn't get 120Hz, and in the end the issue wasn't with the monitor, but either with the cable or recently the buggy MacOS Ventura (a Monterey downgrade fixed that instantly).
You're presuming that Apple is going to force upgrades on you by hiding them in MacOS updates, or deliberately break support for the Studio Display in future MacOS versions.
No, I don't think that. But when you are a regular customer that is told to make sure to install updates regularly, they might just install these as well since they are part of the MacOS updater. Apple won't have to deliberately break anything, I agree with you that this is of course nonsense. Apple will just move the monitor to "vintage" status. They did just this with the LED Cinema Display from 2008 and 2010, brightness control no longer works with the latest Apple Silicon Macs, you can attach the USB cable and it will show up in the System Profiler as connected, but the brightness controls are dead. If you bought that display in 2011 and bought a 2021 MBP 10 years later, now your display is stuck on 100% brightness.
For some people the 3rd party MonitorControl software allows to change the brightness still by sending commands to the monitor itself, but it doesn't work for everyone.
And that's what you might be looking at with the Studio Display. People are going to attach their shiny new 2031 Macs to the Studio Display and something will be broken. Perhaps it's "just" the brightness controls. But perhaps that entire single USB-C port with that extra complex firmware won't be able to communicate with those latest Macs anymore.
I have no doubt that a regular DisplayPort adapter cable in 2031, let's say a USB-D or USB-E to DisplayPort one, would work just fine on any of my regular iiyama monitors (or whatever brand you got as long as it isn't something terrible like Gigabyte that has issues all around).