Yes, that's just how it works. Do remember to close it before you
> refill the system!
>
I've never never seen one here in The States. (Under the sink above the shut-off valve.)
If you really need a supply-pipe drain, a better location it seems, would be at the lowest point on the pipe. You might have to shut off the water main to drain the pipe, but big deal.
What a weird rule, I'm glad we aren't the only ones who come up with weird rules like that.
I've done many plumbing projects and the only time I've drained the water line is if I'm going to disconnect anything low in the system where there is significant water above, or if I'm going to be soldering. What little there is above the shut-off valve under the sink is barely anything.
Cut that thing out if it's necessary for your project... you nor anybody else will NEED it ever.