Test flight with test pilots, intentionally stalling at 3,000' (instead of 10,000').
Not quite , there were not test pilots , otherwise they would not attempted this test like they did on the approach leg .
from the accident synopsis :
The primary cause of the accident was that the crew attempted an improvised test of the AOA warning system, not knowing that it was not functioning properly due to the inoperative sensors. They also disregarded the proper speed limits for the tests they were performing, resulting in a stall
But your reasoning is correct , this cannot be compared to the 2 Max accidents, as as the aircraft been normally flown it would never have stalled, or dive/trimmed into the water.