Inconsistent arm length is only proof that someone might have issues with reference sizing, not AI. Webcomic Pixie and Brutus had it so bad the artist made it into a hilarious joke and then stated they'd finally make a size reference chart to keep it consistent in the future. Freaking animated series Steven Universe, a professional production, constantly had issues with not just limb lengths but size consistency as well. Size consistency is the worst reasoning of them all if anything.
The flowers in the background could just be that the artist has issues with distance perspective / drawing. A lot of artists who don't do backgrounds have that issue.
And like I already mentioned, the best evidence so far would be the blur lines surrounding the character, which would be evidence of AI in that they added the character into these backgrounds, but not only could that also be just a standard blur tool (because the artist isn't good at backgrounds), but it would be weird that someone using Ai to make this would go through all the work of training a custom LORA or model on this character specifically, but wouldn't reduce the size of blurring in the parameters when inpainting. It's possible, sure, but usually someone who already went to the lengths of learning how to train a model or such to achieve such consistent results would also quickly look up how to set the inpainting parameters to not show such a massive blur line.
But the other thing to note that this might not be AI is the aspect ratio. Presumably this would have been done as separate panels on AI, and then you'd crop if needed and make a fake comic panels. If so, why would you crop the edges of the comic / leave them incomplete? Usually that's specifically where an artist of this type of comic panel would sign their work too, if they chose too. Cropping out signatures is something commonly done by people reposting work done by real artists, and has been an issue for years as well.
Now, all this is too say that it's not definite that this is made by a human. The point is that there's no strong evidence that it's AI. The clothes are consistent, the shoes and fingers are as well. That there's 5 fingers is actually suspicious, but it's definitely something an amateur artist would choose to do.
To me, the most likely case is this is a mix of AI and real drawn work / lots of manual editing work (for example, the mouth in panel 2 and 3 look the same, indicating it may have been copy and pasted by hand rather than generated). But my second guess it's purely drawn work with a lot of manual editing. What I can say is this is very unlikely to be 100% AI.
This is better evidence, but still would be difficult to keep such consistency with the character. That would be quite the advancement itself.