They are doing the fight because they think it is in their best interests. But that doesn't necessarily mean winning.
Andre is going to have to work to get the win. He is not going to tap him out in 30 seconds or something like that. It will take an effort and probably take a little while. Ryron will probably "survive" for some time.
The tricky part is that "surviving" for 10-15 minutes does not mean the fight is close. However, the Gracie camp will spin it that way. The fact that it will take an effort from Andre to win is going to be spun as a victory.
Ryron is never going to threaten Andre in the least. He will just defend and stall the whole time. That is his strategy. It will work for a little while, but eventually Andre will find a hole and get the sub.
A lot of people will take that as evidence of a close match. The rest of us will know better and understand that it is not a close match when no offense or threat is mounted, no matter how long it takes to be finally broken down.
Andre is going to win a match like this 99 out of 100 times. It may take him 10-15 minutes each time, but he is still going to win it. The Gracie spin strategy will be to make it seem like it was a close match and Ryron would have a roughly equal chance of winning a rematch.
If Ryron submits Andre, it would dramatically change my entire view on BJJ. But I don't see that happening. If I'm wrong, I will eat my words.