Screen readers with touch screen support typically include a "touch exploration" mode where you can tap or slowly drag around the screen and listen to feedback on what you're touching, before it activates. Setting aria-touchpassthrough on an HTML element indicates to a screen reader that touch events targeted at this element should be passed through directly, instead.
Screen readers with touch screen support typically include a "touch exploration" mode where you can tap or slowly drag around the screen and listen to feedback on what you're touching, before it activates. To actually activate, you double-tap. There are a few cases where this is undesirable - like a virtual keyboard, or a signature pad. In those cases you want gestures to be passed through directly. Some native accessibility APIs already have a way to specify this, like UIAccessibilityTraitAllowsDirectInteraction on iOS.