It was pointed out to me that my Cheat Sheet and Wandering Creature Prep Sheet do not factor in Surprise when determining the encounter distance. This is a feature, not a defect! While it has been engrained in my head that encounter distance and surprise are formally linked together, that is not the case, as I discovered when I went back to look at the original b/x rules and the Old School Essentials version.

From the 1981 Basic D&D rulebook (bold mine):

SURPRISE: After finding the number of monsters appearing and their distance from the characters, the DM should then determine whether or not each side has been surprised. It is possible for both parties to be surprised! Sometimes there will be no surprise, due to the situation.

The Old School Essentials basic ruleset is actually less clear in this regard. They do not mention distance in the text regarding Surprise but do muddy the waters a bit (though emphasizing the GM's ability to modify the mechanics to fit the context) in the section on Encounter Distance:

The situation in which the encounter occurs often determines how far away the monster is. If there is uncertainty, the encounter distance may be determined randomly:
▶ Dungeon: 2d6 × 10 feet...

The bottom line is that in OSE and Basic, there is not a specific surprise distance range. Distance is a simple 2d6 x 10 feet and, if one party is surprised, the other gets a free combat round of actions before the surprised party becomes aware.