If an employee is entitled to 'sick days' and sick pay, it is the employee who should determine what constitutes 'sick enough' to miss work.
In my years as an air traffic controller, I was once challenged by a stupidvisor on a sick day call. He was satisfied with my response of "there is a difference between being sick enough to come in and watch people control air traffic, which is your job, and sick enough to feel unable to come in and control air traffic, which is my job. I will let you know when feel that I can not perform up my own personal performance expectations".
It is not the employer's call. And certainly not the role of a machine to make the call.
And now for the new, improved 2.4 version of..."No one could have forseen..."