Could you elaborate? To me there seems extremely little overlap there (I'm familiar with both the procfs and linux's ptrace APIs, but not OpenBSD's ptrace).
Interesting. I didn't know much about /proc's original design intent, and Wikipedia indeed says "the design of procfs aimed to replace the ptrace system call used for process tracing", citing https://lucasvr.gobolinux.org/etc/Killian84-Procfs-USENIX.pd... ("Processes as Files", USENIX 1984)