Perhaps. But how would he know that only a Bijuu could stand up to his Susanoo? Because that implies his Susanoo fought a Bijuu before. We know bringing out Perfect Susanoo is not a trivial matter to Madara, and that he would only bring it out in an important fight (i.e. VOTE). These are just some of the things which are going through my mind.well it is possible that they both got stronger. there was a good time period between konohas founding and madara and hashiramas fight at VOTE. a year or 2 is more than enough time for a ninja to get stronger. tobi was able to fight perfectly fine with the kyuubi out. minato implied that there was some sort of time limit though but im not sure. but tobi was able to control 5 tailed beast(although he almost lost control of 1) purely with eye power. i feel that madara could fight efficiently with the kyuubi out for a good duration of the fight. the only reason that tobi couldnt fight alongside his beasts is because, he was also controlling the beasts through stakes and the user has to remain stationary to control the paths. if tobi can fight efficiently using only tailed beasts then there is no doubt in my mind that madara can fight efficiently alongside the kyuubi.
In any case, I know that Hashirama is up there with the very best. He could be the strongest, I don't really know what Kishi is planning to reveal next. But I think the idea that he is on his own tier is incorrect.