Don't be too bothered. Movies with a much higher budget than the land before time made worse mistakes. It may even be possible that some inconsistencies are the result of cuts from the movie (the original movie is not the only one from which scenes were cut) though I admit that this is extremely unlikely in case of the pictures accompanying a song. However, it is not the kind of plothole that will bring an entire movie down.
True then theres the fact that this tends to show that even now lbt is not useing the rubber stamp meathod of doing backgrounds and accessory forground parts as so many animated films have done from late 80s to now.
What is intresting as he pointed out though is how they decided to simply mke cera move foward to make room when originally they would not have needed to do it had the log been same size through out hehe.
Guess they were hoping to sneak that by the viewers

To landbeforetimelover
Best advice i can give try to avoid tareing apart the films to much less you can do so with out being to annoyed. Theres alot of this in pretty nearly every animated film every made. I my self enjoy looking for these little things. They dont anoy me but its intresting how they will change a scene to fix little errors like scale of a scene item such as the log. It shows that to change that log and fix it would take along time and shows its all hand drawn vs stamped.