Yes; but what is your point? A congested network like you describe isnt ever going to reliably carry realtime communications anyway due to latency and jitter. All you could reasonably due to 'punch through' that situation is to use dirty tricks to give your client more than its fair share of network resources.

6kbps is 10x less data to transfer than 64kbps, so for all the async aspects of Messenger or WhatsApp there is still enormous benefit to smaller data.