I don't think he doesn't notice it. First of all, he included the decorated tree in the scene - there was no tree when Hank left or when he invited the girls to dinner. Therefor, I would assume this means that the Tramp bought and decorated the tree himself. Secondly, the Tramp gets the presents he intends for the girls from under or next to the tree when he is setting the table. I have both the 1925 and the 1942 versions - maybe it is more noticable in the 1942 version, I can't remember. I know that Charlie used different footage for many scenes or replaced some from 1925 to 1942.
Lori