This has been bothering people for a long time. You can find complaints about it in the lists going 20 years back. In my opinion, it is a bug. Part of the problem is that anything that is defined in boot-9.scm is public.
The builtin has never been documented. We should deprecate it and eventually remove it. For anyone who uses it, the fix is trivial and backwards compatible. The deprecation process we have gives people plenty of time. Maybe we should advertise more loudly what the deprecations are. But we should still do it. Daniel
