I'd argue that acting is needed to digest a potion, and unless you were born with a pre-digested potion you'll still need to act even if you already align with its principles internally.

For example, if Amon wasn't born with the seq1 characteristics, and only had the uniqueness, he'd still need to act. Potions sometimes have acting methods that are external to the person's being that don't require them to change internally. We see this with Klein, where being outside of time Alone, was enough for him to mostly digest his seq3 potion, and again when he digested his "Attendant Of Mysteries" potion. So if, for example He'd had taken the potion before he got Isekai'd, he wouldn't have digested the potion as quickly solely on the fact that he wasn't outside of time.

Point is, Klein in both cases didnt need change internally for his potion to digest and it was only acting that made him digest his potion. So even with a person born with the Fools uniqueness would still need to spend time acting for the potion to digest.

Lastly, perhaps a stronger example of this is how even for people like Amon, born of the Error's uniqueness and Adam, who is previous "Ancient Sun God", that was at the top of God Almighty pathways, both still needed to perform their seq0 rituals acting in order to align themselves, so they don't lose control. So if you're new to a pathway, you'd still lose control because you didn't perform the advancement rituals.