Would you agree it is safe to say these older square d breakers are not intended for 2 conductors? See 2 pictures below.
Yes I definitely agree.
I agree with Christopher
I like referencing this article. Those breakers do not appear to be designed for two and I cannot make out the label.
These are old style QO Circuit Breakers. You should never put 2 wires (double tap) the breakers.
This may have been done because you have run out of room in your panel.
Here is an easy solution. Purchase these half size breakers (2 individual circuit on the same size frame)
The part number is QO2020. You can not use QOT2020, they have a hook and will not fit.
I state 20 amp because your existing is 20 amp but you must check your wire size.
…if the label says they are allowed in that location, that’s good.
A pigtail and a wire nut within the cabinet is a much easier and cheaper solution.