UPN, or Universal Process Notation, is based on IDEF0 (https://en.wikipedia.org/wiki/IDEF046) which is a systems modelling approach which works really well for complex systems, especially where you have complex human systems.
UPN was about simplifying the approach to make it easier for 'normal people' like me to understand it easily and therefore use it to reach a shared understanding as Colin described.
One of the objectives when we started Skore was to go further in making it easy to use for the widest possible audience. We blended UPN with User Stories to make it as conversational as possible.
So the origins of the approach were not designed specifically with Gherkin format in mind but has evolved to address the same need - making things clearer and easier for people to understand collectively.