That's... DUMB.
I use rainwater catches to provide water for my animals. The roofs which catch the rainwater are well away from trees, to reduce leaf matter and the like. The drain pipe has a mechanical filter to further reduce same. Water is stored in a 250+ gallon food grade tote, painted with layer upon layer upon layer of white paint - both to deal with my temps here in FL (91 today), and to prevent UV penetration to keep algae down. The lage volume keeps the water (for me) from ever freezing, while working as a large thermal mass to even out temp swings. If I'm 70 at night, and 90 during the day, that ton of water I have in storage stays at a nice 80 degrees.
In persistant sub freezing temps, one must either use a heater, or a small pump in a closed loop system (so none of the water freezes till ALL of the water freezes - which takes "a while")
and yes, the system should ABSOLUTELY be made with a cleanout/flush at the end of the run. Some bleach on occasion, and periodic flush outs.
Whomever made the thing pictured seems to have used a pressure reducing fitting for a garden drip water irrigation system (completely unneeded, a gravity fed barrel - even one the size of mine - has almost negligible PSI), a length of garden irrigation hose, a plastic elbow guaranteed to split in the first freeze, and a piece of PVC which might suvive the first freeze (only because the plastic elbow fails first) which eventually gets plugged with dirt for lack of a proper clean out.
and yes, there is a non-Zero but entirely negligible chance of HPAI transmission, if droppings on the roof arent hot enough, long enough, before being washed into the storage container, diluted to some infinitisimal amount, then potentially consumed by the birds. I've not done the math, but suspect its close to the chances of my raised coop being struck by lightning, with consequence to alkl the birds inside.
apologies for tone, the sun took it out of me today, and my back hurts. I'm not a good human in the best of times, and today is not the best of times.