grayway2 By the end of 2023, Apple said that they were not aware of any successful attack against individuals using lockdown mode : https://techcrunch.com/2023/12/07/apple-says-it-is-not-aware-anyone-using-lockdown-mode-got-hacked/
So since then, I did not find real public proof of devices running last iOS update + lockdown mode on being exploited remotely
Apple would say that because why won't they. They're a marketing-oriented company, first and foremost.
CitizenLab (Canada) is more humble in its assessment (in the same blog post you shared):
Given that we have seen no indications that NSO has stopped deploying PWNYOURHOME, this suggests that NSO may have figured out a way to correct the notification issue, such as by fingerprinting Lockdown Mode.
GrapheneOS It doesn't enable a bunch of advanced hardening features.
Yep. Inexplicably, iOS' Hardened Runtime remains opt-in, instead of turning it ON in Lockdown Mode for all apps.