We've had to make compromises, and that's a good way to work when people have different ideas.
There is no doubt that the line from the Irish kings back to Magog is mostly fictional. The Irish kings are only documented back to about 600. Before that, there are a thousand years of names that weren't recorded until the 18th century, which happens to be a period of wholesale genealogical invention.
There is also no doubt that whoever invented the Irish line back to Magog was trying to hit the Biblical Magog. Unfortunately, the two Magogs ended up living hundreds of years apart. If you went through the Irish line and tried to guess at birth years, you could not get back far enough to line up with the Bible. There is no way to make them the same person.
Even if we think there might have been an oral tradition, we would have to think that it was perfectly preserved for 3,000 years. That no one ever wrote it down, even though they wrote down other less spectacular lines. That never once in 3,000 was anyone ever tempted to add, change or invent any part of the line. And, that the Irish somehow preserved a tradition that shows the Bible is wrong about the dating . That's a lot to ask.
Even though the line is mostly fictional, I agree that it is worth preserving on Geni. Even if it's an 18th century invention, it's now part of our collective history. We have a text. We have no way to prove or disprove it. So, like good genealogists, we keep a copy in case we find something else. But -- it's not possible to connect the two men.
One major problem is that Geni looks for the shortest line. So, someone with this line through the Irish kings would always find a line back to Adam through a fictional descent. In other words, Geni will ignore lines that have a greater of being right (arguably, depending on your religious beliefs) in favor of this one that is certainly wrong.
In your own genealogy program, you might want to connect the two men and ignore the problems. But on Geni, we need to remember that thousands of users share this same line and have very different opinions.
To solve the problem, we made two Magogs. There is an Irish Magog and a Biblical Magog. You can follow the Irish kings all the way to the Irish Magog, then if you're interested, you can click the link to go to the Biblical Magog and follow him back to Adam.