I don't know if the person got her question answered but I have a couple of thoughts. Dell has a driver download for its pen, Though I believe the screens are the same there are two different xps one is a 2 and one which screen folds back to use as a tablet and normal one. I'm not going to trace down to see if they are the same screen but it maybe possible that they are different.yet still be xps 9070. the other small thought is I would bet wacom or whoever makes their pens is the same company that makes Dells.
Small thought is also sometimes manufactures run out of certain parts so they replace them with others. Perhaps Dell had more of the digitizing screen than the normal one at one point and just used them for a short period. As for "who would use a pen on something that doesn't fold out" I find it is actually easier for myself to use a pen instead of a mouse on my lap top. I don't want to carry around a mouse and sometimes, on the go there is no place for one. I have problems using touch pads for certain things and a pen to be able to write quick notes for stick um programs is a great help. For myself the pen is easier to use for many basic point and click things also. I just wish the bamboo would work on my 9560 with 4k touch screen. I do wish Wacom and dell would communicate better so it's easy to tell if the pen works or not . At the moment if you call wacom you usually get a "I don't know it isn't listed on our list.Instead of a more definite" I'm sorry that pen needs to work with a digitizing screen and the one you have is just a touch pad style" Support is a dying art I think.
I can't find it now, but I saw a tweet by Frank Azor from around the 9570 launch time where he confirmed that XPS 9570 will use exactly the same 4K display with digitizer support as XPS 9575 2 in 1.
So, it's not just some random parts, but if a specific pen works on 9575 2 in 1 with specific drivers then it should work on 9570 because they have the same display. But 9575 has an "official" Dell pen support, whereas 9570 doesn't. However, the display hardware is the same.
I think you may want to reconsider such a sweeping statement.
"However, the display hardware is the same."
change that to,
"On some units, the display hardware may be the same. It's not guaranteed to be so on all of them".
We have two XPS 9570 and one 9575 at work with the 4k UHD display. The Dell PN579X stylus works on all of them but you cannot install the Wacom driver on the XPS9570 to personalize the pen features beyond Win10 options.
That's really a shame that Dell won't allow the pen driver installation on XPS9570 system because the display is strictly identical to XPS9575. There is no technical justification behind that. I really hope this gets fixed ASAP because the XPS9575 is too limited to be used as a mobile workstation.
The XPS 15 9570 with 4K touchscreen uses, at least in some cases, a Wacom touch sensor that is interoperable with a stylus that uses Wacom's AES protocol. These include Dell's own stylus (which supports both Wacom AES and Microsoft's MPP), Wacom's own Bamboo Ink, and at least some of Lenovo's styli.
I got myself a Lenovo GX80K32884 at half price from Amazon Warehouse, considering I may have to return it, and it worked fine out of the box. Both buttons are distinctly recognized. It comes with three replacement nibs.
Of course, YMMV, as I have seen no guarantee that every XPS 15 9570 does use a Wacom digitizer. Mine had no indication that it did.
Oh, and don't believe what you read about a feel as good as writing with a fountain pen on parchment: it feels exactly like writing with a plastic pin on a glass surface. But that is OK.
I recently got the active pen from dell and it works out of the box on xps 15 9570 4k. I just cannot start the pen control application where I can control the other features. But everything works as it should.