He's 6'2 and apparently shockingly strong to his opponents. Maybe he's not big in the era of Chris Weidman and Luke Rockhold, who cut a ton of weight to duck LHW, but that doesn't mean Okami isn't/wasn't a big MW.
Okami has never really been such a big MW. By today standards, he is definitely not big.
A decade ago, in his first year in UFC, Yushin was fighting Rich Franklin who had easily 10 pounds on him fight night. Okami was fighting at WW before the UFC and didnt cut much to make 185
Around 2010 when he was training in America he put some mass on him in the gym but still, I recall his training partner Sonnen saying Okami walk around much lighter than him. Around that time Yushin also fought Munoz or Boetsch, guys way naturally bigger, thicker, than Okami. By that time the Rockhold and Weidman were already around.
Now, at 36, he is fighting at 170 even for a Pancrase/DEEP payday so I doubt he suffer that much to make weight
Also, yes he is 6"2, but also his reach is 72" which is actually below average, and has also a pretty tight waist and lanky legs. He has a huge head thats true.
The walk around weight is a more realiable source than the eye test anyways.
About his notorious strenght, it may be true, but just like some other guys have big power relative to his size.