This is a picture of a 10-ton header we built.
Now the header is for a residential property, with a bunch of (expensive) ball valves fused in line. Commercially, an engineer would likely specify the design with a focus on flow optimization and may end up with the same layout. For residential, one would commonly bury the header after pressure testing.
In this case, we also need to think about service calls. It is highly unlikely that a service company is going to show up at a residential property with a 5hp purge cart. Most of us typically carry 1.5 to 2 hp purge carts.
So you spend a bit more money up front allowing one to isolate individual circuits for future maintenance. In the end, we can purge and setup this system with the existing circulating pumps. We don’t even need to take the purge cart out of the truck.