Looks as though Serif have seen the light and intend to make a corrected installer according to this on their Forum.

Gerry

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System: Win 10 Pro (21H2), Asus X99-E WS, CPU i7-5930K -3,5 GHz, 32 GB DDR4 2666-16 RAM, NVidia GTX 1080 Ti GPU - 11 GB VRAM(Driver Studio-536.99), Samsung 850 Pro 512 GB SSD, 6 TB HD storage.

Sorry,
the browser went crazy with my last post.
The text is at the bottom at the end.

Hello Robert,
Yes, I have Vers. 2.0 and do not have MSIXinstalled but immediately unpacked and with Photo.exe started the program,
entered the license and activated it.With iCl 7 & 8 the image is saved directly via Save sent to iCl
but must be cached for CA4.
With regards
Günter

Sorry, I thought I was in the German forum.

Hello,
I don't think that the problem is with Affinity ( apart from the msix file),
rather with Reallusion because it works fine with iCl7 and 8. In A-Photo I clicked on Save
in A-Photo and the changes were immediately displayed in iCl.
Günter

Hallo,
ich glaube nicht das daß das Problem bei Affinity liegt ( abgesehen von der msix-Date),
eher bei Reallusion weil es bei iCl7 und 8 einwandfrei funktioniert. In A-Photo auf Speichern
geklickt und die Änderungen wurden sofort in iCl angezeigt.
Günter

I worked out the the message from 'danielpojda' and made a step-to-step guide for my own lesssons about CTA5. (English is not my natural language).

Thanks danielpojda... Your steps outlined here are what I surmised, and as such, we miss out on the two way link for the SVG file.   It's really no different from creating a new AD file, without launching from within CTA, exporting your file as a SVG file, then opening CTA5 and dragging in your new SVG into the scene.  Then when saving the SVG anew in AD, it should update in CTA, but with AD it doesn't. 
As shown here, for Adobe Illustrator...
https://www.youtube.com/watch?v=9kS1C9UBInQ

Hi - I'd like to try this but am unsure of the following step in the process.
"Then I took the exe to install."
What does this instruction mean?  'took the exe to install'

thank you and best wishes

You can achieve this by replacing default.svg in the source location.
0. Click on affiinity icon (launch to affinity designer)
1. Click new object
2. In affinity draw your object
3. ctrl+s or save file -> copy destination to default.svg file
4. ctrl+shift+alt+s or export 0> chose svg and click Export
5. paste destination and click save
6. confirm replace 
7. Click prop
8.  :)

Thanks Peter.  rosuckmedia's solution did the trick, and was a lot easier and perhaps safer.
I'm curious though, about using SVGs with Affinity Designer, since it cannot save the currently open file in anything other than an Affinity Designer file (.afdesign).  Would the workflow, in that case, not provide a two way trip, but instead will require one to actually export the current file as an SVG, and then drag that into CTA5?