Sylas' auto attacks don't stack press the attack while he has his passive [GAMEPLAY]

I recently played a game of Sylas and found a very strange thing.

For whatever reason his auto attacks, while he has his passive stacks, don't stack press the attack. While this might also be an intended interaction I'm pretty sure that it's not. His passive gets triggered on basic attacks which should proc press the attack normally.

I know this doesn't sound like a huge problem, but I wanted to experiment with Omnystone Sylas and the fact that press the attack is a practically dead rune for seemingly no reason just feels bad.

As for how to reproduce it... just take press the attack on Sylas

Edit: I tested it with other keystones that require basic attacks (Like fleet footwork, hail of blades and grasp), all of which behaved normally and triggered from his empowered attacks. This only further makes me believe that this interaction is not intended.

Second edit: Because of how his passive works, Black Cleaver doesn't stack either. This obviously works as intended because it is only supposed to trigger on physical damage and his passive completely transforms the damage to magic damage. However this might (for some reason) be the cause of the issue, depending on how press the attack works in detail (Whether it requires the target to take physical damage from a basic attack)