I leave the first room, he's right there. I find a tesla coil, he's right there. I find SCP-970, he's right there.
I find a tunnel, he's right there.
I die, he's in the loading screen.
Edit: Just did a full playthrough on a livestream. I saw SCP-173 twice.
SCP-173's spawn rate seems to have been amped up in 1.1.5...
#1aaaaaaaaaaaAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA