First of all, the map appears to be completely unreliable not because it was not designed by Tolkien himself, but rather because its author tried to put together a "composite" map representing all "the lands of Arda throughout the ages", which is an impossible task to achieve.
So, the map shows:
- the two Great Lamps of the Valar Illuin and Ormal, long destroyed by Morgoth and ruined with the surrounding lands before the First Age started
- Beleriand, which sank beneath the sea at the end of the First Age during the War of Wrath, which also heavily changed other regions of Middle Earth
- the continent of Numenor, raised at the beginning of the Second Age and then submerged again (with the exception of its highest peak) at the end of that age
- the Undying Lands, removed from the Circle of the World after the destruction of Numenor
- parts of Middle Earth as they appear during the events of The Hobbit and The Lord of the Rings (at the end of the Third Age)
To make a silly comparison, it's as "reliable" as a map of Earth showing together Pangaea, Atlantis and present-day Europe :-).
Moreover, as commented by user @suchiuomizu, Numenor appears completely different from the map published in Unfinished Tales (redrawn by Christopher Tolkien from a sketch of his father's), where Numenor is shown as a large star-shaped continent whose central region is a large plain with an isolated mountain.