OneDrive activity limit reached despite extreme rclone throttle

I am using rclone to transfer files to OneDrive at 1990s dialup speeds:

rclone sync --links backups remote:backups -vv --onedrive-chunk-size 10M --bwlimit 200K

It transfers some files but then gets this error:

pacer: low level retry 1/10 (error HTTP error 429 (429 Too Many Requests) returned
body: "{"error":{"code":"activityLimitReached","innerError":
  {"code":"throttledRequest","innerError":{"code":"quota"}},
  "message":"The request has been throttled","retryAfterSeconds":74,
   "@error.X-ClientErrorCode":"quota"}}")

Why does OneDrive throttle the requests when rclone is already throttling them down to basically nothing?