For humans binary searching a dict is slower because it requires a different physical action vs. scanning and we have advanced OCR and flipping through capabilites. Especially recognizing when something hasnt changed e.g. still on Es keep flipping is maybe 10ms.
No the point is you know exactly where T is just by looking at the dictionary (or at least, you learn this if you use a dictionary a lot).
IOW your prior on the data distribution lets you skip the first 4-5 binary chops.