Headtube length is reasonable with these modifiers-
frame era- 60’s bikes will most often have more generous clearances, and often a longer top tube- making for a shorter headtube verses
an 80’s bike with tight clearances for only smaller tires and a short reach brake in front.
One gets a visual Ref. After a while.

I have been fooled, but not often.
worst was a reportedly 57 center to top frame that looked “right”. It arrived and was a 54!
even marked as such on the bottom bracket.
the image was distorted- very strange.
referencing the images later it still looked like a 57 in the seller’s sale image set.
seller went awol after.
Vanished.
fortunately it was a good size for my son later.