Oh how I wish this was true. We have customers sending 10-100s requests per second and they will complain if even just one gets 429. As in, they escalate to their enterprise account rep. I always tell them to buy the customer a "error handling for dummies" book but they never learn.
I don't have an answer, but I wonder, for the sake of protecting your own org, is some sort of "abuse" policy the only approach; as in, deal with the human problem, be clear with them in writing somewhere that if they're seeing response X or Y (429 etc) that they're essentially abusing the API and need to behave.
And we’ve had cases where we had “fuckoff” charges in contracts (think $1 per API call after X thousand calls a day) and the customer just gladly pays tens of thousands of dollars and thanks us for fixing their problem.
The money is nice but sometimes you just want to shake them and say “look we have notifications you don’t need to poll the endpoint ten times a second, fuck it give us the code and we’ll fix it …”
There's just no winning sometimes sigh.
Well, if this is a supported (as in $) account, sure enough, have the API rate limits published and tell them in the most polite way to RTFM