Look carefully at your link. The name is "CFP NATIONAL CHAMPIONSHIP" game on the link you provided, NOT the NCAA National Championship game.
According to the NCAA, there is no NCAA sanctioned NCAA National Championship game. The "College Football Playoff National Championship" game is the national championship for the 4 teams invited to play in the CFP invitational competition, which has nothing to do with the NCAA, but is just chosen by committee. The NCAA says schools may claim a "national title" if they are ranked as #1 by any of the NCAA recognized 30+ selectors, which UCF has done. I believe 4 of the NCAA selectors promised to award their #1 ranking to the CFP winner, but at the same time, many others are based completely on what the computer says is the best team, and not the opinions of a committee. And those computers, officially recognized by the NCAA as a selector of those who can claim a national title, are picking UCF as #1, which makes them a national champion, just like USC in 2003, and Alabama many times in the past.
For those claiming the national powerhouses would be made fun of for doing such a move, Auburn 3 years ago created a committee to determine if they should declare 3 additional national championships based on certain polls having them #1 in past years. And Alabama did the same and added 3 additional ones, including those not even recognized by the NCAA. I agree its a crappy system, but its the rules Alabama plays by, that Auburn plays by, Georgia plays by, and now, UCF decided they will play by the same rules as well.