That account requires an email address for whatever.
ICANN regulations require registrars to collect email addresses, and that apply to gTLDs, but ccTLDs have often similar constraints, so that the registrars and the registry can contact end client in case of problems.
With the current legal frameworks (GDPR and the like), it is often hidden in whois output, but not always. Do a whois on apple.com
and you will see what email address they used.
Nothing special there, anyone is free to use any email they want.
Also big companies, and for example for hidden/not announced project, often used proxies to register names, like attorneys or their registrar acting on their behalf.
What specifically triggered your question of
If this is true, what email do large companies/corporations use to buy their domain name?
Anything particular in mind?