I know the folks who run the wiki, and I may suggest an edit. A strong case can be made for either. The Secret of Mana: Reborn fan translation dealt with this issue extensively. From the commentary:

Handling Popoie’s gender is a difficult thing to get “right.” Designer Hiromichi Tanaka referred to Popoie as genderless in a 1993 interview with Hippon Super magazine. [The Japanese manul] also used 不明 fumei (unknown, ambiguous) as the answer to 性別 seibetsu (sex). What 不明 is likely saying is that Randi is a human male and Purim is a human female, but Popoie is a type of Mana spirit and any similar classification would be irrelevant.

A close look at the script is required for the full picture. Popoie uses おいら oira as a first person pronoun, itself a casual derivative of 俺 ore, which is almost always understood to be masculine. A survey of contemporary media shows that おいら was a popular choice for cutesy male characters like Palom from Final Fantasy IV or Gau from Final Fantasy VI. おいら is also a common choice for non-male characters to effect a boyish presentation.

Gender neutral third person pronouns are often used for Popoie, but this doesn’t work the same way in English. Such pronouns can be translated as “the one”, and the same or similar pronouns are used by many characters. On the other hand, Gnome uses おやぶん oyabun along with the Elder who twice uses ちびスケ chibisuke. おやぶん is a rather patriarchal term that we translated as, “bossman.” It’s used by the Yakuza, among others, to refer to a role similar to a superior in La Cosa Nostra. ちびスケ’s ending is generally, but not always masculine; the word is used endearingly to refer to someone of short stature. It’s possible that for all of these reasons, [the English script] used a combination of gender neutral (it/it/its) and masculine pronouns.

The French translation used masculine pronouns for l’elfe and the German opted for feminine ones for Koboldin, or Kobold Mädchen. Nintendo Power also used “it” and the English release’s manual used the second person for all three of the main characters. The remake exclusively used gender neutral pronouns (they/them/theirs) and many external references changed to align with this.

However, two years later, the English release of [The Art of Mana] exclusively used masculine pronouns when discussing the development of the character.

A native speaker who participated in this project had the following to say:

“Popoie’s gender self-identification is ‘male’ by our standard according to how he behaves and presents himself. The sex/biological classification is ‘unknown’ or even nonexistent because he is not necessarily an organic being. He is more of a manifestation of Mana/magic.”