Vader

Hold two fingers on the canvas while resizing.

So as you can see i have been able to do what you want. 
Take a look at the photo that shows you why you are not getting the inversion.  You must select the image first before you can invert the selection.  From that point on your have the selection made as you can see in the channels tool.  From that point on you can apply anything to your inverted layer as long as it is not embedding itself into another adjustment.  

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Not doing anything with layer selection in the example provided though initially I tested with base layer selected (worked as example) and then with not layer selected (as shown in recorded example). I concluded it doesn’t matter as long as initial selection was made with base layer selected and while in Selection persona. Then it’s just a matter of inverting the original selection. See layers below.
The trick to this is that you must still be in Selection persona or else you won’t get an invert option following the long press.
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I’m getting a new invert adjustment layer. I'm not sure I understand your issue. Your screen recording shows applying a recolour not an invert?
You might like to check out the Resources thread. I have uploaded a PDF version of the Help file that you can read in PDF viewer or in iOS books without closing Photos current work screen.
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Hi Vader,
A question, are you applying the recolour to the inner selection, then trying to invert the selection so that can apply something to the area that surrounds the inner area where you applied the recolour?
I remember a tutorial quite sometime ago where this process was shown, but quite frankly I have never been able to apply that technique myself.  Generally what I have needed to do was to create a new recolour layer and then apply the inverted mask.  
If this indeed a bug and anybody has the knowledge as to how this process is supposed to work, please let us know.   
With thanks, if that is indeed the issue that Vader is trying to understand.

If that is what the OP is trying to do? Try this:
1 make selection and apply recolour adjustment.
2 long press on screen and select invert selection from pop up menu.
3 apply invert adjustment.
Original selection is recoloured, rest of the picture is inverted colour.
Affinity is non destructive so it will create a new invert mask in addition to the recolour mask. You can invert a mask (in Channels studio) but it will simply apply the original adjustment to an inverted selection.
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DM1, I can’t see what you are doing with the layers.
Vader, is this what you are trying to accomplish?

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