So this code is disgusting.
https://github.com/Blood-Asp/GT5-Unofficial/blob/7b592a645c91bd5f3ef76189af7936908b427301/src/main/java/gregtech/common/tileentities/machines/multi/GT_MetaTileEntity_ProcessingArray.java#L67

Proposal: replace with a dynamic map, this is to be done directly to GT via a PR, however, it will also be added via ASM to previous versions. Other mods can register machines and recipe maps via the GT++ API, to avoid GT versioning hassles.

Result: machines such as the Simple Washer or Dehydrator can be used within the PA.

Fixed in Blood-Asp/GT5-Unofficial#1551