He said it MIGHT be true, not "we believe Vayne's range should be nerfed to 525". That is not an absolute statement; Morello is saying if Vayne needs nerfs a way to do so MIGHT be to reduce her range by 25.
Also, Vayne cannot interact past 550 range. I'm not sure why this has to be repeated every single thread, but her range is 550. She CANNOT interact past that range; if you are 551 range away Vayne can do literally nothing to you. Every other adc has a way to interact past their autoattack range (Jinx WER, Ashe WR, Varus QER, Kog'Maw QER) except a few (Tristana, who instead gains range per level and has all her skills increase in range with her, and Twitch, who has a MASSIVE range steroid to make up for it). Vayne does not.