I agree that hexcrawl rules were not as detailed as rules assuming the party was in a dungeon. However, you are assuming a somewhat static dungeon where monsters wait behind doors for PCs to discover them, and many of the better adventures of that time neither advised or allowed that. DMs were encouraged to create movement in the dungeon, to restock it, have the enemies use tactics as if they were defending their homes, and so forth. Not to mention, the DM is assumed to literally create their own dungeon in 1e, so I’m not sure I agree with what you’re saying about the players control when encounters occur.