It's an urban legend perpetuated by electricians. They would not bear the UL listing label if the backstabbing feature were not safe and effective.
So UL limited backstabbing devices to 14 AWG based only on an urban legend?
I think not....
As for Wagos and other connectors, I use them but not on the neutrals of multiwire circuits.
That is a puzzler, you feel they are good enough to use but not good enough to use.
I consider all my splices to be of equal importance.
