User blog comment:Obyvvvatel/The 4 gold attributes of jungler champion./@comment-5980721-20130211174722/@comment-5266525-20130212231357

It doesn't count because there's a difference between a mere heal and actual sustain.

In order for something to really count under the blanket term of sustain you need to be able to consistently keep your health high while jungling. Empowered W only comes up every 5 Ferocity points, points which you can now no longer use for ganking or increasing your clearing speed, and your cooldowns are high early anyway meaning those five points are few and far between. Rengar cannot commit to constant farming early on at all with just his W to hold him up.

Saying otherwise is like saying jungle Soraka has good sustain (which she doesn't - too long a cooldown and it has a low base heal early on).