Hey, this was about 1971. Not many engineers were climbing inside their suppliers' ICs and studying the layouts. If you didn't, though, you could be stuck with a lousy layout. Connecting them properly in parallel, you can get the linear gradients of Vos, to cancel. And the gradients in beta to cancel.
Any linear gradients caused by imperfect die attach tend to cancel.
In this example, the transistors are still connected as an ordinary differential pair. But if you connect the transistors to act as a current reflector by shorting Cl, Bl, and B2 together, and merging that metal, the interconnections become very simple. I looked at their results. When I apprised them of their error, they tried to argue that the magazine's computers had misrepresented their results. They did not understand that their computers were clueless.