F2 horn non-latching for North American locos is sort of important. It's really hard to do a level crossing sequence otherwise!
Now as to what controls the latching, I've noticed in the past that JMRI server has a settings page that lets you latch or unlatch any function key. Yep, it does need a separate router, but that's not too hard to implement. Because JMRI allows this and has a roster that can be downloaded to my UWT-100 I am inclined to be using JMRI and not YD7001 Wi-Fi. I wasn't intending to start JMRI on the layout, but I might have to now.
Karst says the throttle is in control of the latching but I've only ever seen that implemented as an option on the Digitrax DT602D which is only compatible with the LNWI. No other throttle I've seen ever (including phone apps) mentions F2 latching - including the UWT-100.
Digitrax and NCE control units both have F2 non-latching for their proprietary throttles probably because they are aimed at the USA market.
Oldngrey