Regarding rain detection:
It wasn't so long ago that Hall devices would have been out of the question because their current draw would quickly run batteries down. These days there are some pretty neat devices available which can run with microamp level current drain.
One advantage these have over reed switches is that there is no fragile glass-to-metal seal to be stressed with every thermal cycle, and no moving parts inside. Solid state, rugged, but yes they cost more than reed switches.
As I look at the pics in the filing, I see some interesting clues
There is a side view pic of the tipping buckets. It appears to have a familiar arm and magnet, as you would need with a reed switch rain detector. There is a reed switch shown in the photos, and , other than the wind direction encoder, nothing I could identify as a Hall device.
The main board has a two pin connector labelled "rain". A small board has a two pin connector labelled "water", same as on the little connector board that has pads that press against the metal rods in the rain gauge.
It is as if, in this one device at least, rain counts are done with a reed switch, but counts are only enabled by the presence of water.
It will be interesting to see the final hardware.