Help with how the 4th coolant bleed point behaves. The so called "jiggle valve"

I've been reading and watching a few videos on how to bleed my MGF 2002 and I came across this guide: https://www.mgfcar.de/bleed/index.htm

It shows a picture of a valve with the hose removed. No coolant pouring out of it even though the hose is removed.

So I went to the engine head, removed the jubilee clip and tugged off the hose. This created a water-fountain-like jet of water which surprised me as I thought the function of this valve was to release air not water. If this is a incorrect assumption can someone correct me? I'm not 100% on what the author is trying to explain to do.

TL:DR The author mentions the valve should be checked if its blocked. I seem to have the opposite problem of it not blocking anything.

Edit: the specific hose i'm referring to is ITEM 7 in this picture: https://www.the-t-bar.com/cooling-heating-air-conditioning/100-cooling-pipes-hoses-expansion-tank/308-expansion-tank

edit2: I've done some more research on a Caterham website and its seems like this "outlet by the throttle" sticking open is a common issue and as long as its releasing water its not gonna do any damage. Can someone confirm this is the same for a mid engine car like the MGF and this isn't the reason why my MG is cooking itself during an emissions test?

https://www.caterhamlotus7.club/forums/topic/37637-watercooling-circuit-diagram-for-k-series/

Have you tried a vacuum filler to extract and refill the coolant ? They are quite cheap now and are reccomended for ensuring the cooling system on rear engine cars is correctly filled without airlocks

That jiggle valve can get stuck closed and prevent air escaping from the head. If it is working (or stuck open) air, then coolant will flow out. That's normal.:yesnod:

Legend. Thanks all. That's all I needed confirmed!