My Wally World had a similar rule and I liked it.
If you are sick and cannot work find someone to cover, then this will not count against your attendance.
If you are sick and you do not find anyone to cover, then it does count against your attendance.
Depending on how many occurrences an employee had on there attendance tracking, they could be perfectly fine if they miss a few days here and there and do not cover there shift - life happens, everyone should understand that.
This rule was put in place for that TM ( that we've all worked with) that would call off on there opening shift every Saturday or Sunday and would even attempt to look for someone to cover thier shift. They would call in and say they are "sick", but if you creep on there Facebook or listen to gossip around the store you will find out that they were out partying and is just a little hung over.
Now... If you call off and can't find a replacement and you ended up going to urgent care or something. The manager could take the occurrence off the record.