I've noticed something odd with this function. If I set the SSID authorization field to false I get a result back in ~1.5-2 seconds but if I set authorization to true I have to wait between 30-40 seconds for the response. Tested in postman with same results.
I can get round this by making my urlfetch calls async but its not ideal.
So the time is just less than half for this smaller network, if network size definitely has something to do with it then the next step would be to determine if its number of WAPs or number of clients that is effecting it. Usually more WAPs = more clients, I think I'd have to wait until a weekend to have the same number of WAPs but less clients to test that theory.