https://www.folklore.org/Signing_Party.html
So no "of course" about it.
Note also that Microsoft had a "no easter eggs" policy starting in the early 2000s. It's not really a Jobs thing.
- the effects of it are clear
- there's basically no chance of unexpected side effects (I suppose in theory it could structurally weaken the case if the signatures were carved too deeply...)
- if a user stumbles upon it the intention is pretty clear and obviously harmless
- it's not something that might get snuck in without approval of senior management, because it's not hidden in that sense, so there is a limiter on how many of them accumulate and how complicated they might get
which help to explain why you might by policy forbid software easter eggs while still being an advocate for "signing your work".
What people will put up with in a hobbyist and small business environment is very different to what's acceptable in enterprise and beyond. It's all fun and games until someone has to sell to the US government...