So then we have to check if flespi sends reduced messages.
To test it, we can use, for example, a https://ngrok.com/ service with a free account, to expose some local test HTTP server (like
npx serve .) to the public internet.
So I did that test locally, and started ngrok inspector app shows me such an image:
So flespi platform sends me more than 10 keys in the message.
I strongly suggest you to check your software using cURL tool I mentioned above in addition to Postman, to repeat your test.