For example the TETRA standard for trunked radio, "The key stream bits shall be modules 2 added (XORed) with plain text bits in data, speech and control channels".

In the TETRA specification they use the term “key stream” to mean the output of a stream cipher, which they call a “key stream generator”. They aren’t XORing directly with a large key - the TETRA key size is 80 bits. See section 6.3.2.2 of https://www.etsi.org/deliver/etsi_en/300300_300399/30039207/...

Yes you can programatically generate a key.

And we call that a stream cipher, not "XOR encryption", even though it uses a XOR operation. You're programmatically generating a keystream, which is not the same thing as a key.