Yes of course all fights start standing but 90% of the time when a grappler gets a hold of a pure striker, it's all done for the striker, even more for a boxer that only has a puncher's chance (a very slightly puncher's chance btw)
I highly doubt a boxer, specially on the level of Floyd only has a punchers chance, if anyone here will be relying on chance, it will be Ronda. She'll bite down on her mouthpiece and hope she won't get knocked out trying to close the distance, which is very, highly unlikely.
Floyd who likes to clinch when things get ugly,
Floyd doesn't like to clinch, he clinches to avoid getting hit, like a fellow poster here already mentioned. Which is the whole idea of combat sports, hitting without getting hit.
and even MORE when you face a grappler that is a judoka or greco-roman wrestler that speciallize on hip throws that you only need to grab the arms for execute their techniques.
I don't think you realize how difficult it is to close the distance on someone with the sole intention to grapple, specially against a high level boxer that is Floyd.
Stylistically this fight is perfect for Ronda and a nightmare for Floyd. Ronda won't stand still in front of Floyd like Tim Sylvia did against Mercer because judokas always look for a grip ASAP. Floyd is serving himself to her for his love of hugging, the perfect position for a judoka to work, arms grabbed, hip throw, position, submission.
If your comparing Ronda to Sylvia then you should also differentiate Mayweather from Mercer. Both Tim and Ray were out of their primes and Ray still managed to knock Tim out.