The options are not presented as options, that is what I mean. You get monsters in a specific environment, often in a specific situation. Like 3 Lizardmen arguing around a campfire. Now the players need to weigh their options, for example: do they try to sneak around, surprise them, intervene in their discussion as peaceful mediators or as instigators, listening to their discussion to find out more informations about the whole fraction or their specific needs so they maybe can offer them what they need/want etc. Or just attack them, but that is their own choice then. Nothing in the adventure or in the game-design requires you to kill the lizardmen.
In 5e all these options would've been spelled out to them and non-combat encounters are often specificially declared as such. In Shadowdark and OSR in general its often vice-versa, that combat-only encounters are specificially declared as such and all others are implied to be open to other approaches. That is one of the main reasons unfamiliar players and DM struggle with OSR games, because there is much more active thinking, improvisation and participation required, every encounter is a little sandbox.
Combat is considered a fail state in OSR, it happens when your other approaches failed. You tried to instigate a melee between the arguing lizardmen but they saw through your manipulations and attack. Or you tried to sneak around them, but they heard something came over to investigate. When they questioned you they realized you came with ill intent to rob them and they attack you. Combat is dangerous and thus to be avoided. If it erupts, you did fail some other attempt in most cases.
