And you are probably right, but thats like saying that if you are blind or deaf your not the intended user. More often then not people don't get to choose whether or not they have access to the internet. Its an accessibility issue. Excluding users for things that are outside of their control is not right.
There are obviously accommodations and functionalities that are unreasonable to implant when it comes to accommodating accessibility issues. But offline functionality is not one of them, not for time tracking.