Since you can Help, then move away and the Help action still works,
Would the opposite also be true? So if someone were to use the Help action on an enemy creature, and that creature were to move away, would the next attack on the creature still have advantage? Heck, would the OA from another ally within 5 ft of it have advantage as the creature moves away?
As already clarified in your linked tweet, it doesn't matter if you move away from a target after distracting it - your allies still get advantage on the first attack against the creature - so it's obviously not the case that you need to remain standing next to the target for an ally to gain the benefit.
Further, the benefit of the Help action lasts until the start of your next turn, regardless of what the enemy does in the meantime:
If your ally attacks the target before your next turn, the first attack roll is made with advantage.
Even if the enemy takes a whole turn before your ally actually gets around to attacking it, your allies still get the benefit on their first attack. Whatever you did to distract it only stops working on your next turn, not theirs, and moving away from you doesn't obviate the effect.
The attack doesn't have to be on your ally's turn, either - it's simply the first attack any of your allies make against that enemy - so it would definitely apply if the enemy provokes an opportunity attack by trying to move away (though if it simultaneously provoked several OAs from different allies by moving, only the OA resolved first would get advantage, and the creature whose turn it is gets to choose in what order simultaneous effects are resolved).
The Help action used in combat only says the creature must be within 5'. This applies at the time you take your action.
The link you provided confirms that it doesn't matter if you move away afterwards, so by extension it doesn't matter if the creature moves away either. (It's all relative, as Einstein would surely agree!)
The Help action also says:
If your ally attacks the target before your next turn, the first attack roll is made with advantage.
It doesn't state that this attack roll must be on the ally's turn, only that it must occur before your next turn. It would thus apply if that ally managed to get an opportunity attack on the distracted creature.
