I would guess the small emoji are never meant to be expanded in a normal use, whereas the stickers scale up and down as needed, having a better resolution at different sizes.
Hello @d4raxx ,
Thank you very much for your suggestion. Your suggestion has been communicated to the developer and the development project manager is reviewing the content. After reviewing your suggestions, we will apply them to the official version if your proposal matches our concept. We appreciate your contribution to the beta program.
One UI Beta Team