Anubis' Passive Lifesteal Scaling Increase does not seem to Work

Sorrow says it grants 33.3% scaling toward magical lifesteal. I assumed that this means any lifesteal is multiplied by 1.33x, so 12% lifesteal would become 16% lifesteal, roughly.

I tried this out in practice. Fairly simply, just get Bancroft's Talon, Pythagorem's Piece, and Polynomicon, and just basic attack something. The number you get shouldn't be anywhere near 47% lifesteal.

Sub....

His abilities apply that Sorrow buff that per tick of your abilities, you get a stack of Sorrow (max 3 stacks). You have to first get 3 ticks of your abilities and only then check. And when fully stacked it grants 100% increased magical lifesteal so you'll get far more than just 47%. You can almost get to 100% if you add Divine Ruin to these items.

It turns out, what was confusing me was that magical lifesteal works differently than physical lifesteal. I feel so cheated; more on that shortly.

I went level 20 Anubis vs Ra bot, had Pythagorem's Piece, Divine Ruin, and Polynomicon, for a total of 50% lifesteal exactly.

I then used a single Grasping Hands at Ra bot. This is a list of the tick damage.

1: 137 damage, gained 22 health.

2: 145 damage, gained 31 health.

3: 153 damage, gained 32 health.

4: 163 damage, gained 34 health.

Test this out yourself, I have repeated this experiment and I can duplicate the results, and you should too. If you notice, none of these are 50% lifesteal.

1: 22/137 = 16.06% lifesteal
2: 31/145 = 21.38% lifesteal
3: 32/153 = 20.91% lifesteal
4: 34/163 = 20.86% lifesteal

16 x 1.33 = 21.28% lifesteal, which roughly fits with the amount I got.

tl;dr: I learned that tick spells calculate lifesteal differently, and it takes only one stack of Sorrow to gain the lifesteal benefit. Apparently, magical lifesteal is divided by 1/3, making it an incredibly useless stat.

Edit: Seriously, I feel cheated as hell. Polynomicon gives a mighty 3.33% lifesteal and Pythagorem's Piece gives an actual 8.33% lifesteal. Just...ugh. You could argue that the area damage/multiple targets counteracts this trait, but teamfights are where lifesteal is usually the LEAST effective.