tau egality in relalivity

What Python doesn't understand.
Python firmly believes that in any case, two observers following different spatio-temporal "paths" cannot have the same proper time.
I explained to him that yes, by affirming that if two observers traveled equal distances, with equal times their own times would be equal (under the condition that the departure of the accelerated traveler is at rest). Python categorically refuses to drink this kind of milk, because he "didn't learn SR like that."
However, it is the good doctor Hachel who is right.
Look closely at where Python and his friends the traditional realtivist physicists are wrong.
Python objectifies the two event points A and B very well, and considers that AB is Tr, i.e. tau, i.e. proper time.
<http://news2.nemoweb.net/jntp?D5sf4f-nI4z2kOO5eZjIDNurKmQ@jntp/Data.Media:1>
Then he will consider the blue curve, which he will think is the other observer's own time.
Here we find our error, the own time of the other observer, it is the continuous evolution of the red lines which at the end of their course, joins the line Tr of the other observer, making the two proper times equal and reciprocal.
R.H.