More than two weeks past, still doesnt work

Same issue occur when the benevolent river spirit is cloaked. So the problem is related to the "turn face up" interaction

I’ve hit the same problem. This issue sticks out very clearly when you have Abhorrent Oculus in the same deck, both of these cards have „As an additional cost…” clauses , but only Spirit triggers when turned face-up (adding the flat waterbend cost to the cards mana cost, which shouldn’t be happening).

I've seen this myself, and the auto-tapper highlights creatures and artifacts as well, suggesting that the additional cost's waterbending features still apply. Regardless, the mana cost to turn manifested creatures face up should not apply additional costs like waterbending.
This also doesn't appear to be a case of the card's mana value being higher as it should be, as cost-restricted reanimation like helping hand can target it as a two-mana creature, suggesting the issue lies with the manifest interaction and not an oversight on the card itself.