But that' s very niche: it is because stealth wards require few secs to be invisible and Leo can overattack them, but here we are talking about pinks after all.
It is a characteristic to consider, but if pinks can be attacked equally by everyone and Jhin takes a whole lot of time to put one down, then i would find it pretty annoying. Also, the OCD strikes in when you miss only a bullet to take a ward down D:
The problem might be when Jhin attacks a green ward with his 4th hit, maybe because he was hitting some minions before, but i would consider that in the same regard as other champions that have an AS boost or AA resent on attacking stuff, like Jax or Varus - also is very player interactive, it is of the player' s care to drop a ward where it can be invisible safely.
Also, i am not sure it is an intended power or weakness for him. Might be however. In the case, i am just letting this notice.