I've mentioned it before, but there is almost always a disconnect between what a manager says and what the employee hears. Both are 100% sure they are clear on the message, yet they rarely are.
One reason this happens is because the manager tries to be "nice". They take into account how they think the employee will respond to them and adjust the message accordingly. The problem is that the manager is usually poor at guessing the response which causes them to adjust the message poorly.
Most often, this causes the manager to be vague, because to be very specific would be insulting the employee. In other words, if you give too much detail, the manager thinks the employee will feel like a child. Possibly, but more likely they will interpret what you ask differently and will not meet your expectation.
The manager tries to be nice and not insult the employee, instead they get an employee who is frustrated because they didn't get clear direction and got negative feedback.
Over-communicate. If you think you are insulting someone, you aren't. If you think you are being nice, you aren't.