How does the benchmarking code add_benchmarks! work on the runtime?

Question

I am trying to understand the runtime-benchmarks gated code on the runtime/src/lib.rs and I realize that we need to "list" and "add" benchmarks that we want to perform : https://paritytech.github.io/substrate/master/frame_benchmarking/v1/macro.add_benchmark.html

However I just want to make sure my understanding is correct:

1. Unless we add it like so in this code :

add_benchmarks!(params, batches);
add_benchmark!(params, batches, frame_system, SystemBench::<Runtime>);

it's benchmark won't be found or run when trying to run using benchmark subcommand right?

2. Why is add_benchmarks!(params, batches); needed? It seems to me the odd one out as all other add_benchmarks! usually list a pallet and it's alias beside it.