Typed bonus to splash damage does not use base alchemical bomb damage type

[pedrogrullada]

PC2 introduced a few typed bonuses to splash damage (Expanded Splash and Alchemist's Goggles with status and item respectively), but when these are added using Flat Modifier, instead of using the damage type of the bomb, they become untyped damage. If the bonus type is untyped instead of circumstance, item, or status, then the damage type works as expected, using the base damage type of the bomb.

Here is the rule element used to reproduce the issue.

{
  "key": "FlatModifier",
  "selector": "alchemical-bomb-base-damage",
  "value": 1,
  "type": "item",
  "damageCategory": "splash"
}