Players who memorize stat blocks from other systems expect predictable encounters. Open Dungeons breaks that pattern. The DN may read that the Divine Sentinel has "Radiant Authority" listed in its special defenses, or some other ability the stat block might not spell out exactly what that means
The DN decides what it means: maybe it's a commanding presence that forces a Wis Mind save or the character flees in fear for 1d6 rounds. Maybe it's an aura that makes lying or deception impossible within 30 feet. Maybe it lets the sentinel issue a single command that must be obeyed unless resisted.
The same goes for abilities like that are mentioned but with not details i.e. Elemental Nature, Damage Immunity, etc. Let's take Teleport ability as an example. If the stat block ability doesn't mention "once per day, 60 feet, line of sight only..." the DN can interpret it based on context. In a tight dungeon corridor, maybe the sentinel blinks 30 feet to flank the party. In an open temple courtyard, maybe it vanishes and reappears 60 feet away on a balcony. The mechanics serve the story, not the other way around.
You may find these abilities in Special Defense or Special Attack and discover their details in their About sections.
Creative Freedom for the DN
This flexibility isn't vagueness - it's intentional design. The DN knows their table, their players, and the flow of the encounter better than any rulebook ever could. If "Radiant Authority" needs to be a devastating effect against a high-level party, it can be. If it needs to be a minor inconvenience for a low-level group, it can be that instead.
Stat Block = Function
About = Inspiration
DN Interpretation = The Final Word
When in doubt, ask yourself: What would make this encounter memorable? What fits the tone of this creature? What keeps the players on their toes? Then rule accordingly. The stats are guidelines, not shackles.