They are wrong though. Every pro asked about the best server said Isner, it's not particularly close, Isner has a good case for being the best server tennis has ever seen - he definitely is on clay and slow high bouncing hard courts by a huge distance.
Every pro in the video you watched
Not saying he doesn't but you said what 6 pros all said Isner? Maybe the top 100 were all asked and they only showed the 6 that said Isner because they had an Isner bias. Maybe 94 said Raonic
Don't believe everything you see