I honestly don't think there is one. On the other hand, though, the Social and Exploration rules map really nicely to Milestone Experience (not Story-Based Leveling that people commonly call Milestones). Just award a Hard Encounter's worth of XP for the triggers they list (or two encounters if it's a tier above). I appreciate having the triggers, and I think it'll help ensure my players and I are on the same page about what Milestones are supposed to achieve.
But, no, I don't see a good reason to use the 100 point scale (and a few good reasons not to).
I actually just re-read the experience section in the DMG.
I was mistaken about Milestone Experience... it is Story Based leveling that I have experienced in the past and disliked. The 5E DMG provides plenty of guidance for non-combat experience awards.
I think you are right that we probably don't need the revamped XP scale, but I do like how this system does explicitly break out awards into the three pillars and includes treasure as a part of exploration. As you implied, this is something you can put in front of your players and state this is what you need to do to get XP in this campaign, and just let them loose.
I'd probably incorporate the new document's Tiers (provide at least 4 but probably more) but use existing XP award recommendations... perhaps equate each Tier to a Hard Encounter XP amount for a set level (Tier1 = a Level 1 Hard Encounter, Tier8 a Level 16 Hard Encounter, etc).
Exploration Milestones:
1. Discover a new location in the wilderness - Tiered based on distance or difficulty to reach.
2. Discover a path to the next lower level of the dungeon - Tiered based on level depth.
3. Discover a sublevel or secret area in an known location.
Treasure Milestones:
1. Retrieve a significant horde - Tiered based on value or maybe just award XP for the GP value of the treasure, old-school style.
2. Finding a 'named' weapon or 'naming' a weapon you possess. - Tiered to power or legend of the item?
3. Finding artifacts important to cultures and institutions of the world. - Tiered to the age of the artifact.
Social Milestones:
1. Establish Friendly relations with a significant faction or NPC - Tiered based on strength of the faction.
2. Overcome a Hostile reaction from a significant faction or NPC - Tiered based on the strength of the faction.
3. Learn a significant lore from a social interaction with a faction or NPC - Tiered to the obscurity of the lore.
Combat Milestones:
1. Defeat or overcome a challenging foe - Tiered to encounter difficulty (Medium, Hard or Deadly... no experience for easy or trivial encounters).
2. Overcome and resolve a threat to a friendly settlement or homestead - Tiered to the size of the settlement.