Rather than this, I'm hiding the Submit to CQ button while the CL is in WIP mode: cl/161729269

what's the point of letting the users press one button more? i.e. if you already got your review +1 and want to land you need to press "start review" even though somebody has reviewed it already...

This adds more formality, but less practicality.

But I have no strong opinion here.

The issue is with process: The first notification that people on WATCHLISTS receive about a change existing is "hey it's being submitted to the CQ".

Ack, the watchlists argument makes sense, though I believe that in practice the people following the steps from the description will 1) start the review process, 2) wait 0 seconds, 3) press submit, so that it de facto won't make a difference to the watchlist folks... But lets keep it that way so that people maybe get more disciplined with their process.

Would it not make more sense to send the notification (at the latest) when the first review +1 arrives?  That way the notification has a better chance of being noticed before the commit.

And this is probably the wrong place, but I'd like to quibble with the wording "Start Review".  This sounds like the button you would press to start reviewing the change.  In fact the person who must press it is the one person who can't start reviewing.  How about "Ask for reviews"?

Yeah, definitely the wrong place, go ahead and file that bug at go/polygerrit-bug. Also potentially worth filing a bug about automatically starting review when the first votes come in, just to have a discussion about it with the appropriate gerrit stakeholders.