DMT in an indole
psilocin is an indole
psilocybin is an indole
melatonin is an indole
bufoteine is an indole
seratonin is an indole
pinoline is an indole
harmine is an indole
harmaline is an indole
LSD in an indole
LSA's are indoles
5meoDMT is an indole
ibogaine is an indole..
and many many more..
So I dont think it's just an indole thing.
Ibogaine and harmine/harmaline share very similar structures..it is well understood that share some similar binding in the brain and that they also share many of the same psychedelic effects. This is probly why they both produce these same sorts of tracers.
Long live the unwoke.