OK sure. :) I guess what I meant was, if you're setup for booting Pis, you can't also boot arbitrary PCs without extra work.

The issue is that the Pi does something that is almost-but-not-quite PXE. In particular, the RPI firmware does not send anything that identifies itself as an RPI so that the DHCP server can determine what packet to send in response -- the option 60 string it sends in the DISCOVER packet claims to the DHCP server that it is an X86 server running in legacy BIOS mode. The only way the RPI will boot is if you send it that extra magic option 43. For those of us that write DHCP servers that try to be intelligent about how to respond to PXE requests, the plethora of stupid not-exactly-PXE mechanisms the various ARM SBC hobbyist boards are annoying as fuck. At least the server class ARM stuff usually has a UEFI implementation that adheres to the UEFI extensions to the PXE spec and properly identifies itself with options 60, 93, and 94.