What "variable reward" actually means
A slot machine doesn't pay out every pull. It pays out unpredictably, on a schedule tuned to keep the machine profitable while keeping the player uncertain whether the next pull is the one. B.F. Skinner documented this as the variable-ratio reinforcement schedule in the 1950s — the single most resistant-to-extinction reward pattern known in behavioral psychology. It's why slot machines are engineered around it deliberately, and why so are Instagram's and Facebook's notification systems.
Neither app tells you what a notification contains until you open it. "Someone liked your post" could mean one person or fifty. A comment could be warm or it could sting. The Reels algorithm — present on both apps — curates near-miss content: close to what you want, not quite, extending the search rather than satisfying it. None of this is incidental. It's the same mechanism the state filings are pointing at when they reach for the casino comparison.
Named, not implied — and Instagram says it more directly
This isn't DarkBadge reading a metaphor into the case. The mechanism is named directly in DarkBadge's own scoring rationale for both apps. Facebook's: "The algorithm uses variable reward schedules to withhold full satisfaction... The algorithm deliberately withholds completion to maintain anticipation." Instagram's rationale goes further, naming intent rather than just effect: notification timing is "explicitly A/B-tested to maximize FOMO and anxiety," designed to "find the moment you were most likely to feel FOMO." One reviewer's account, cited in the scoring notes, describes checking likes on a new post as "waiting for a slot machine." That's not DarkBadge reaching for the casino comparison — that's the product's own users reaching for it, independently of any court filing, and independently of each other.
Where the comparison holds and where it doesn't
A casino has an exit — you can leave the floor. Instagram's and Facebook's notification systems follow you off the app, onto the lock screen, into every idle moment the phone is nearby. The reward schedule doesn't require you to be sitting in front of the feed to fire. That's arguably the more aggressive version of the same mechanism, not a looser one — and on DarkBadge's own numbers, it's Instagram running the more aggressive version of the two.