We only rebuild the ISOs periodically. Since the kernels get constant updates and non-LTS kernels have such support windows, the ISO kernel will frequently be EOL. However, if you do an online install(Which is the most common choice), it will install the latest kernel, not the one from the ISO. If you do an offline install, the kernel will be updated the first time you update.
As for your original question, here is an answer I wrote sometime back: