WFM API 429 Rate Limit during Bulk Schedule Export

Can anyone explain why the GET /api/v2/wfm/schedules/{scheduleId} endpoint returns a 429 status when I hit it with 10 concurrent threads in JMeter? The docs state:

“The WFM API supports up to 100 requests per minute per tenant.”

My load test script is only sending 60 requests per minute, yet the gateway drops half of them immediately. Is there a hidden per-user rate limit I’m missing?