The baby humanoid chestplate was added with a properly centered model, but the latest preview changed it to one that is offset, despite the changelog stating the opposite.
It did have an issue with baby piglins and zombified piglins, but that’s a problem with their model rather than the chestplate (tracked in MCPE-237446).
The new model is now offset for all mobs. To fix this issue, the erroneous chestplate model change must be reverted.
Notes: Every baby humanoid armor piece has some minor model issues, see MCPE-236696.
Current release:
Latest preview: