Why is it allowed to have the faucet inside the beer when serving cask ale?

Finlandbrews said:

When serving draught beer from kegs the faucet should never touched the beer when serving/pouring the beer into the glass. I would presume that wether it is cask ale or draught beer there should not be any change. However in an introductory video about the Beer conscious program together with the support of left hand brewing the person demonstrates a cask ale pouring and he puts the faucet into the beer?

Why? And why is it allowed with cask ale and not keg ale?

Thanks for feedbacks!

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