That's exactly what's going on. In a bit more detail: when a POST arrives and no receiver is available yet the server lets the sender know that it won't handle any more data (TCP Zero Window). When the receiver connects to the server the server asks the sender to continue writing and the data is relayed (proxied) from sender to receiver. If multiple receivers connect they're put into a queue and the server waits for the sender to POST the data again once the ongoing transfer is finished.

An interesting difference is that in the browser the rePOSTing is done through scripting whereas when using cURL or Wget (or httpie, or ...) the server will issue a 307 Temporary Redirect allowing cURL/Wget to send the file again without manual intervention. Hence the name! (although that doesn't really account for the "Station" part yet)