pj, I size all my photos I save for "email/forum use" to the largest side being only 850mp and other side(s) auto go less using photoshop. But, yes it did say that it would, I guess 850 is OK anyway. No real answer to your question. The smaller photo was a smaller photo size than the first which was 850 on top and bottom.
I created my own personal album.
MP, I guess I am dense, but my main reply box at the bottom of a last post in a thread does not have a blue upload file box per your example, I just have Post Reply and More Options blue boxes. I may be taking a short cut or doing something odd but that's how I have always replied to posts. Help is appreciated.