Maybe this is naive or startup-brained of me: I understand not wanting HR-related things to be potentially exposed by a misaligned agent, but when it comes purely to the building of software I personally do not care at all who can read the code/discussions & engage with the process.

Totally get that for code! But there are orgs where non-code things are compartmentalised — maybe for leak reasons — that still want to employees to make use of agents.