As to general siphon (not the brand you are talking about specifically) there was a Peet Brother's a couple decades ago that emptied with a siphon and a friend who had one was constantly futzing with it to keep it clean of nesting creatures of all sorts. Maybe the implementation by your manufacturer has eliminated many of those concerns.
I have an RM Young siphon that is pretty good when it rains occasionally (none for over two weeks here) and while evaporation is small, it is a factor especially when temps are in the 90s a lot. Measuring it when it falls is a great idea (tipping bucket) but I know one of the reasons that Young made a siphon was for unstable platforms, like buoys and such where tipping buckets wouldn't work.
In some instances the contact sonic method (Vaisala WXT sensors) which are amazingly accurate in my experience, measure instantly and no emptying required. Also there was a variation of having collected water run past a sensor (continuity drop or light beam) which measured a known sized amount of water in a different way. I can't even give you any names at this time since I don't know if those are even produced any more, or got left in the dust by more reliable methods.
Great discussion, and I appreciate learning from those who comment here.
Dale