How the Arcane Boots + Soul Ring trick works?

I've been playing Techies quite a bit, and in all the video guides I see on YT I see them doing this trick with the Arcane Boots and the Soul Ring that's never fully explained.

It looks like they're dropping the Boots, activating the Soul Ring, and then picking up the Boots again, and this somehow gives you more MP.

I tried it out in a couple of games and it doesn't seem to make a difference. It seems like a bug, and I'm not quite sure if it's been patched out, or maybe I'm just not performing it correctly. Could someone explain how this is supposed to work?

Solution 1:

When you gain intelligence or +mana in DotA, it sets your new mana total such that it's the same percentage as before acquiring the item. If you have 50/100 mana, and your mana pool increases to 200, the game sets you to 100/200 mana to maintain the same percentage.

In this specific case, let's assume a mana pool of 500 with Arcane Boots equipped (+250 mana), and you have 200 mana remaining (200/500, or 40%). You drop the Arcane Boots, reducing your mana pool to 250, and your current mana to 100/250 (40%). You then use your Soul Ring, giving you 150 mana, putting you at 250/250 (100%) and pick up your Arcane Boots. The game looks at your mana percentage, and adjusts you to 500/500. After eight seconds the Soul Ring boost goes away and you drop to 350/500, essentially netting a "free" 150 mana (based on the 200/500 you started with).

As for whether this is a bug: like most confusing things in DotA, it's kinda just how the game works on a fundamental level.