Updating a day later in Mojang is quite a normal event. Snapshot 17W49B includes a small list of bug fixes and tag optimization. As promised earlier, the tags features expand and become more user-friendly, which makes data packs a very interesting change.
Full Snapshot 17W49B changelog – Minecraft.net
Mods will also not be left out, and very soon we will see new optimized recipes and achievements included in the modification and resource packs or allocated to a separate category – data packs for Minecraft.