>>35782542>>35782710Only the head placement seems to differ at a closer look. While on the final they restored the original head placement but fixed the angle on the rest of the body.
My theory is that
>>35782542 didn't make for a good silhouette, so they redrew the sprite like this
>>35782710 in order to make the silhouette stand out more like you see on the title screen of the prototype. Then after they were set on the final title screen, they thought Ho-Oh's sprite had no business in looking like that anymore so they restored the original pose, as previously mentioned.