The lens blur tool is the first one of these AI tools that really sort of troubles or bothers me. I think this is because - no pun intended - it seems to ke that it really starts to blur the lines between what is authentic and what isn't, or maybe more to the point between what is truly "of the artist" and what is from a machine.
Previously, you could use AI to do a few things, one of which was inserting new elements in a photo. This is a pretty clear line: if you're concerned with the authenticity of a photo, you're not going to want totally new things inserted into it. Or, if you see a photo you know had something inserted by AI, you know that the photo is ultimately the work of a machine. This can also apply to removing things using AI by generating a background.
Now I think there may be at least some gray area here when we're talking about very small things. I don't consider a photo any less the work of the artist if someone removes a twig from a photo (though maybe it does bother you). It doesn't bother me that much if someone extends the edge of a frame by 5% or something by generating a background. It would make me look at the photo differently if someone removed a whole bunch of foliage and generated a third of a bird to fill in the gaps. It would make me look differently if someone extended a frame by 50% and added a whole background scene in there.
I think what it comes down to is whether the final product represents a photo that is substantially the same as the original, or if they're creating something of an entirely different character. A minor extension of the edge to give a subject more headroom or make the composition look slightly better is the sort of thing that could easily be something as natural as the difference between the VR element re-entering before a shot and slightly changing the framing from the original. A change like this doesn't bother me because the final product has the same essential character as the original. Most people would look at the two photos and say, "that's basically the same photo it's just framed slightly differently." The same applies to a photo with and without the single twig in the way.
I'm not saying that there's no element of skill involved in getting that composition perfect in the first place or getting the bird without the twig in the original image. There can be, but ultimately I see the difference as so minor that it doesn't strike me as "no longer the same photo."
There are edge cases. In one example I remember Duade Paton had a photo with a nice setting sun the top half or so of which had been cut off, so he extended the frame to put in the rest of the sun. That's a harder case because in some ways the change was essential to the character of the photo. I think some would be less okay with this than others.
Having played with it a bit, I think this new tool really blurs the line even more than Duade's sun. I am not at so I can't share it now, but earlier I took an old shot of a heron in flight which was always pretty mediocre and blurred the background and it's like a totally different photo. Many of us on this forum who have spent a lot of time around nature photography have heard Steve and others talk about the fact that at levels of skilled wildlife photography the photographer is usually looking at the background first and foremost even before considering the subject. It's that important - so being able to take just about any background and turn it into a great background is, to me, often going to really completely change an image to the point where it's really just not the same photo.
On the other hand, there's a degree to which someone might reasonably say that this is just sortof functioning as an extension of a photographer's equipment and is giving them the chance to do in post what they already would have intentionally done in the field if they weren't prevented by economics. I can't afford an f/2.8 telephotos lens, but if I could, I'd have one and that heron would have been photographed with that nice background in the first place, so did I really change my photo's character, or did I just get the equivalent of a much more affordable fast aperture?
These sorts of dynamics and questions leave me feeling pretty uncomfortable about how to view photography in a way other advancements haven't.