I think competitive board games are quite different from recreational board games in nature and draw different communities. The typical questions asked in the proposals for go, chess,... are very different from the questions asked in the existing boardgames.SE. In each of them the commenters were against a merge into the normal boardgames.SE.
There is a similar discussion atGame specific sites but it's more in the light of a merge with boardgames.SE, and not a seperate site for competitive boardgames.
IMO the difference is similar to the difference between SO and ComputerScience.SE, physics and theoretical physics or the two math sites.
The focus is typically strategy and becoming stronger. There are tournaments and for several of them even a scene of professional players. A typical player puts hundreds of hours into a single game instead of spreading it among dozens of different games, like it is common with recreational boardgames.
Currently there are several such proposals for games like go or chess. But it looks like all of them have a hard time getting enough committers.
The main problem I have with such a merge is that there is relatively little overlap between the individual communities, even if they are similar in nature.
Should these games remain in different proposals, merged into one competitive board game proposal or even into the normal board game community?