Pumpkins that were stored in any container are converted to Carved Pumpkins in 1.13. That shouldn't be the case. Pumpkins should remain Pumpkins.

Example:

Someone has 3 double chests of Pumpkins before upgrading to 1.13. Probably stored for trading with farmer Villager. After upgrading, he now has 3 double chests of Carved Pumpkins with basically no use for them.