"But Fayte", I say, "what about the times this happened in NPoT?" I'll give you Tachibana, someone who was introduced in chapter 20 and didn't even start going all-out until chapter 243, but for the rest I'd say there are indeed comparable cases in the sequel.
For instance, Oni had a match in ch 4-5, but he only played with the cross-string racket. The next time he appeared, he was shown training with the strongest of the camp and left one of the strongest MSers on the floor. We then saw him obliterate some HSer at the end of the team shuffle, saw him just below Tokugawa in the 2nd string list, then he went on to defeat the No. 5 of the first string. We didn't see the extent of his power until the second match with Kintarou in ch 91.
It's even more apparent for Tokugawa. In his very first appearance he's compared to Yukimura, one of the very strongest characters we had known until then. He beats Ryoma without really breaking a sweat. But we don't actually know anything about his abilities until he plays Byoudouin in ch 115.
And let's not forget about Irie. Out of these three he was the first one we saw play a close match, but we still don't actually know what he's capable of even now. Ryoga was introduced in ch 50, we don't really know anything about him. Q.P. got hyped as masterpiece and we probably won't see him again for quite a while; the only thing we know is that he's really strong. Not to mention the other two German pros who were mentioned to exist, but haven't even appeared yet. I'd say Tanegashima falls into this category as well.
So in conclusion, there's been quite a few characters that were introduced much earlier than their true strength was shown.