The administrator account can be renamed which means the hacker needs to figure out two pieces of information : the user name and the password while there is always one root account in Linux named root
Security through obscurity (like "hidding" the administrator's account under another name) at most could delay a few minutes any attack, but does not increase your real level of security at all.
Root accounts usually cannot log in remotely and in most cases their password are disabled by default, so any attack using "root" as username will not succeed on such machines. On the other hand, I have seen plenty of Windows machines that will gladly disclose all the local accounts upon request, letting the attacker know the new administrator's name in no time.
because, strictly speaking, nothing prevents you from renaming root-account on Linux too. the name is just a record in
/etc/passwd file. it might lead to some incompatibilities in software, but that should be rare.
Many flavors of linux (e.g., ubuntu) by default disable password login to the root account, but let the primary account elevate to root permissions by prefixing commands with
sudo and entering that account's password.