A matched set!
No, I did not know that, because it isn't true. Apple was already developing its own GUI at the time of the visit.
Apple developed their windows GUI on their own with some ideas they bought from Xerox for $7 million in pre-IPO stock by observing what Xerox was doing at its Palo Alto Research Center (PARC) in two visits that totaled only 16 hours for six people. Apple took NO CODE and only observed. Steve Jobs arranged the visit because they were working on a GUI and his primary GUI engineer had been one of the software engineers at PARC and said they should see what they were researching there. So Steve approached Xerox' management and worked out a deal to do just that. The two GUIs are very different although they superficially look similar.
Apple, on its own developed movable self repairing windows, drop down and nested hierarchal menus (Xerox's appeared wherever the mouse pointer was), Menu bars, drag and drop copying, as well as drag to an icon to invoke the icon's abilities, overlapping windows, and a host of other features of the windowing GUI that were not at all present in the smalltalk windows that Xerox showed on those visits.
Before you add the myth Apple got the mouse from Xerox that's usually included in this canard, that is also untrue. Apple got that from the Stanford Research Institute, where it was actually invented by Douglas Englebart in the 1960s... and Apple, unlike Microsoft, and Xerox, actually licensed it for their use.
A matched set!