The only thing you read on the wiki-page is the shortdescription that maybe should get reworked? And not all of the rest? I'll give you some examples: "tunnel=* is used for roads, railway line, canals, etc. that run in a tunnel. " or "Where the water from a smaller stream, drain or even cattle crossing passes under a way structure or a building consider using tunnel=culvert in place of the tunnel=yes used for accessible and larger tunnels for roads, railways, etc. " that would apply here. And the next paragraph "When the waterway=* runs underground for a considerable distance, you can use tunnel=flooded especially when the duct isn't designed to be safely accessible in operation or man_made=pipeline for sections built with tube assemblies. " 

and for your initial question for me: Someone asked in chat, i just mentioned that i commented and did a revert but i have to disappoint you, i did absolutely not tell everyone to chime in. 

I'm not the big bad guy you are trying to make me. And i don't think the other guy does get payed for connecting waterways, that sounds like a nice little conspiracy you have there going. But it helps you to just avoid a discussion in the forum. "Everybody else is mean, so i can just ignore them!" 