When the target of a Scrying effect resists with a Will save, the DC increases or decreases based on the caster's knowledge or familiarity with the target. A psychonaut alchemist can create an extract of Scrying, which is activated as a standard action; the DC should start at 13 + their Intelligence modifier.
Potions are like spells cast upon the imbiber. The character taking the potion doesn't get to make any decisions about the effect—the caster who brewed the potion has already done so. The drinker of a potion is both the effective target and the caster of the effect (though the potion indicates the caster level, the drinker still controls the effect).
Suppose the alchemist has only secondhand knowledge of a creature, but the alchemist's friend knows this creature very well. The alchemist then prepares an infused extract of Scrying to target this creature, and this friend drinks it. Does the Will save DC increase because the drinker is familiar with the targeted creature, or does the DC decrease because the alchemist is unfamiliar?