Do Sealing stat increases carry over?

Potential is what you are actually losing. An Aniimo's potential grade sets the ceiling on how far its stats can grow, and a higher grade also means bigger attribute increases every time it levels. Raising Initial Potential through adventure events like the Cross Tea Party is capped at four times per Aniimo, so those four raises are a finite resource you spend on one creature. Sealing it takes them back to where they started.

The practical rule is to decide what an Aniimo is for before you put event potential into it. Party events and the stat increases that come out of them are investment in that specific creature, not in your account. If it is a body you expect to seal later, feed the events to something you are keeping instead.

Stardust is the other way stats move, covering capability awakening, potential upgrades and IV modification. That is a separate channel from party potential, and it is worth keeping the two apart in your head when you plan a build, because what happens to each on sealing is not the same question.

Not settled: How Stardust-bought potential upgrades, capability awakening and IV modification behave when an Aniimo is sealed is not settled. The loss is confirmed for potential and stat increases earned through team party and Sealing events.