https://twitter.com/bkopleck/status/1640398552043257857
only cards/effects like Coin, Formula, Attune, etc count for "when you refill mana" triggers.
the mana and spell mana you naturally gain between rounds doesn't count as a "refill" (this is why Nami says "gained")
https://twitter.com/jonmoormann/status/1640398305468518406
External link →A little terminology specificity here - "refill" occurs when a card or effect gives you mana (not gems).
INCLUDES: Attune, Coins (of course), Formula, etc.
EXCLUDES: round start mana or spell mana (those are "gained," as on Nami's level up), or Crest of Insight