One interesting thing is that this makes closed source code even greater asset for the defenders. Attacker cannot spend tokens for it, but defenders can spend tokens for hardening based on source code, while attacker is stuck with blackbox testing.
You would be surprised how adept SOTA models are at reverse engineering with IDA/Ghidra or even plain old objdump. Opus basically knows IDAPython on the back of its hand.
They can be, but the most interesting parts (backend code, deployment confs) are not usually available. Reversing clients can help to understand a bit, but not with equal level.