While enabling $lookup-$unwind pushdown into SBE, the jstests/core/query/release_memory/hash_lookup_unwind.js test started failing its spill assertions when a $project stage is present after $lookup + $unwind. The failure manifests as:

{{uncaught exception: Error: 0 is not less than 0 }}

on the following assertion:   assert.lt(initialSpillCount, getSpillCounter());

The test works as expected both when running with trySbeEngine (when $project is pushed down as well and we're executing a query only plan) and when we comment out the $project stage. The problem seems to only appear when we're executing the $project in the aggregation layer, and the EQ_LOOKUP_UNWIND in SBE.