It is hugely fun to play with people outside your style, some of my best insights have come from seeing things I'd not even thought of before from playing with 'outsiders'.
When a new student started at Sonny's, their first lesson was usually to get straight in to the flow with him, Sonny would give openings that invited attacks and observe what came out. His only 'instruction' was to grin and say 'Don't kill me, right away OK'? By which he meant keep it light - both physically and emotionally.
He'd go easy at first, then start to 'close the doors', pushing buttons until a general picture of the students personality and tendencies came out.
He was not only learning ABOUT them, he was learning FROM them also.
Often during class he'd just ask - 'Show me some of what you do', and would love it if you explained how something similar was done in another style, either application or body training - By the next week he'd have incorporated the information into his material.
Filipino martial arts have been continually evolving over the generations, and without getting in to the political minefield of 'origins', it is certain that their various enemies were a factor in this. Such it is with all martial arts - you have your style because of who you are, and then there's all the stuff you learn to be able to beat your enemies because of who they are. Others were, and are a catalyst for creativity and evolution.
In fact anyone that is not you is ..... if you learn to understand them.
And a good way to understand them ...? Play with them or fight them.