And even more: if your node’s transmission is received by multiple gateways, you’ll get coordinates of multiple gateways as well. And those could be many kilometers apart.
(You might think you can then calculate the node’s position, but: no. See Location by triangulation for that.)
If you want to access the gateway(s) metadata in a payload format Decoder function: that is not possible. You’ll only get those details using some integration, or by using the MQTT data API.