Unlimited Web Hosting is just a marketing trick to attract new customers.
Are you able to store unlimited data on your 500 GB hard disk?
You cannot as it is not possible, then how can a company can offer unlimited storage on limited storage space. So remember you are not getting unlimited space, but it is just a virtual offer.
Have you ever asked the companies offer unlimited bandwidth a question that with the unlimited bandwidth offered can be used to buffer/ upload / download unlimited data which is hosted on the set up provided?
They will be answering you to read their terms and condition to use the bandwidth consumption. Means you are not able to use this offered bandwidth to access your website with an unlimited users. There are background applications running on the shared web hosting servers to monitor your storage consumption as well as bandwidth consumption.