As I (and others) tried to explain to you before, InfinityFree is not associated with the WordPress.org community. The admin login details for your WordPress site are also completely independent- the WordPress software doesn’t technically integrate with your InfinityFree client area account in any way. So naturally they’re going to have separate logins.
Just for a little clarification, WordPress is open-source software and its versatility (it only requires a database server and PHP) means a WordPress site can be hosted with almost any shared hosting provider. InfinityFree is one of those providers. However, because it’s open source, those hosting companies don’t need to have any affiliation with the developers of WordPress. The forum and community at WordPress.org are run by their own people and are not related to InfinityFree in any way.