Ok I sneaked an opportunity to try this again (it's lunch hour) and confirmed that this is bugged.
I realised that setting the variable to 0 is what disables it in the Options menu, so it should disable it completely with the command too.
I tried it, and sure enough, setting the tooltip wait times to 0 meant that asteroid tooltips are now disabled.
However, only asteroids belonging to an empire other than empire 1 are affected. Player asteroids still display tooltips.
In addition, the UI continues to display tooltips according to whatever behaviour is set in the options menu. It seems like the UI wait time command didn't have any effect at all.
Is it possible to change this with a wuwei import of some kind? It will be a bit of a downer otherwise - I would need to specify in the post with the level that it's recommended to turn it off. Not turning it off leaves my new level with popups appearing every time you issue an order.
It's a minor point I guess but would still be cool to find a way to fix it.. :>