Yes, exactly that. All and every picture I used for training was provided by the artist themselves personally, not harvested by any automatic means. A few were submitted in the KA thread linked above, some by email, and for two specific pictures I asked the artist, and they specifically agreed to that license. All those pictures were licensed to Krita with a CC-BY-KRITA-FLA license (which in very plain language talks about it being used for training by Krita Foundation and its sister company) and the information about it was submitted together with the picture. You can download the dataset from the blog post, you’ll see there are like nine pictures in there, with information about the artists. The blog post itself also links to artists for every picture possibly except for my own pictures (though I think I linked to my KA account too).
Krita doesn’t silently take anything, in fact the only thing it connect to the internet for is to download the list of News and whether an update is available or not. I think on Android there is also the Donator’s badge but I don’t remember how that works, but in that case it’s only for that purpose, too. Krita doesn’t take any of your information, or your artworks, or anything else.
Krita also doesn’t have any TOS, only the GPL license, which has no restrictions about what happens with artworks you make in it, only the source code for Krita itself. This forum has a TOS, and for details @raghukamath would be a better source of information, but there is certainly no data harvesting involved. The images you upload are used to display the images on the forum for other users, that’s all.
You might be interested in this topic as well, it might answer more questions about the design of the tool and the ethics of it and everything else: