That was a deliberate decision, as was the reduction of Ferocity stacks to 4 and the Ferocity generation upon entering fights, and the intended goal was likely to avoid breaking Rengar's flow and requiring him to wait another cooldown cycle for his empowered abilities.
At the end of it, though, that means Rengar's Ferocity system is currently such a poor fit on him that he either needs to end up with downtimes he can't afford to have, or needs to have a guaranteed empowered ability within the first second or so in every fight, regardless of counterplay, simply so that missing one ability doesn't make him hit a wall in the middle of combat. Neither state can be healthy for both Rengar and his opponent, and for that reason I think he might need a different resource entirely: if he generated Fury instead of Ferocity, and generated it with basic attacks, rather than random ability casts, he'd be able to have much more consistent resource generation, while still giving his opponents many more opportunities to deny him his power. Considering how his W and E are also supposed to be used situationally for their CC and utility, rather than rush-casted for more burst, it would also allow him to hold onto those abilities while taking his target down. One of Rengar's current issues, for example, is that he needs to blow his W and E just to access his empowered Q as fast as possible to maximize his burst, which forces him into his pre-rework state where either he or his target loses within the first few moments of combat, with no middle ground. Allowing him to empower his abilities without blowing all of his life-saving utility and CC prematurely could potentially help make him a lot less binary than he currently is.