This is the first time I’ve heard honest statements referred to as tunnel vision.
HONESTY has nothing to do with tunnel vision a lack of a tunnel vision.
Tunnel vision is an issue of perceptual scope.
And dozens of things influence perceptual scope.
e.g. growing up Amish or Mennonite ... or having a serious amount of RAD (Reactive Attachment Disorder) ... or having a very domineering, narrow, rigid parent ... or being unexposed to much philosophical or social variety ... etc. etc.
Tunnel vision also tends to be more common with folks who find security seriously limiting the options and variety they see in life--even at the foundational level of how they construe life.
Honesty has nothing to do with it. Extremely honest people have no or a lot of tunnel vision. Extremely dishonest people have no or a lot of tunnel vision.
Many people have tunnel vision about their pet hobby horses but not so much about other things.
Some people have tunnel vision about most things.