Do you know that your domain’s WHOIS data is public awareness? This is international law and very standard practices. Also, there are services where your WHOIS information is protected, but Short.io does not currently suggest those services.
WHOIS provides information about domains, which are stored in the database on the server owned by the registrar. With WHOIS, you can find out the domain owner’s name, address, contact email, and phone number, as well as contact information for administrative and technical issues.
When you buy a domain, registrars offer to protect your data from unwelcome messages and calls for free or charges.
With non-active whois data, all users have access to your info (phone number, email, address).
The advantage is that you may check WHOIS data of the needed domain. There are free online services to do this. For example, you can go to the WHOIS tool to find information about the domain you are looking for.