Okay – worst subject ever? Sorry.

$ cat ~/.ssh/config
# Host wut
#   LocalForward 1234 whatever:1234

Include ~/.ssh/test.include

$ cat ~/.ssh/test.include
Host op1
  HostName 123.123.123.123

$ ssh -G op1 | grep hostname
hostname 123.123.123.123
canonicalizehostname false

Looks good, right? sshing to op1 would use 123.123.123.123. Yay. Expected.

Uncomment that “Host wut” block. (It could be any directive here. This particular one is seemingly not special.)

$ cat ~/.ssh/config
Host wut
  LocalForward 1234 whatever:1234

Include ~/.ssh/test.include

$ cat ~/.ssh/test.include
Host op1
  HostName 123.123.123.123

% ssh -G op1 | grep hostname
hostname op1
canonicalizehostname false

Wut? Why? Why you no ssh to 123.123.123.123 anymore?

FWIW, if it matters:

ssh -V
OpenSSH_9.6p1, LibreSSL 3.3.6