Answer
This is a deliberate, by-design platform limit rather than a bug — a Projection Delegate/API read task in a workflow is capped at fewer than 10,000 rows and a total response character length under roughly 2,097,152 characters, specifically to prevent high data volumes from causing problems inside the workflow engine, and IFS has confirmed there's no plan to raise these limits. If a workflow genuinely needs to process a dataset this large, it needs to be redesigned around paging/filtering the read into smaller chunks rather than trying to pull an entire large entity set in one unfiltered read.