We are always gathering data to improve the algorithm for future releases. But it will unlikely to be as accurate as a properly maintained tipping bucket. There are so many different conditions that that the RG-11 will pick up that that Tipping bucket will not. Also, since the tipping bucket is a physical measurement of rain, its tough to get as accurate as that.
But, with the current software, the RG-11 is very close. For example, the past data point collections for a TB vs the RG-11 are as follows. These were taken over a rainfall ans then reset.
Hope this helps.
Our manual says to do annual applications of Rain-X for better accuracy, but even more will keep it more accurate.
And here's the table but in mm (if I converted it correctly).