Tal, trying to understand your confused description of what behavior you want to fix required me to experiment and think. There are at least 2 separate issues: triggering of auto-squeeze and lines reported (regardless of what triggers squeezing). The following pair of experiments exhibits inconsistency in both respects.
>>> print('a'*3920) # Fills 49 80-char lines, correctly not squeezed.
...
>>> print('a'*3921) # Wrapped to 50 lines, correctly auto squeezed.
[Squeezed text (50 lines).] # Correct number when reporting wrapped lines.
>>> print('a'*3921+'\n') # Ditto, but not auto-squeezed.
...
# Squeeze manually
[Squeezed text (1 line).] # Different line count -- of output lines.
>>> print('a'*3920+'\na') # Not initially squeezed, '2 lines'.
From msg331784 it appears that you are more concerned here with auto squeeze triggering than with line count. Now that I think I know what you are trying to fix, I can review the code change.
I agree to consider the ambiguity between output lines and display lines, and the effect on line count, later.
Part of my thinking with the simple auto-squeeze formula, besides just simplifying the code, it this. Raymond claimed that squeezing slows down printing. If measurably true, one way to avoid a slow down would be to use a simple heuristic formula to estimate the number of wrapped lines instead of exactly counting. This would be a separate issue, if needed.