I think that was a proposal to allow you to create a new thread to execute a begin block in. and not just a new task, but a new OS thread but I could be wrong?
I do think a macro @withOSthread begin ... end would be useful and I like using a name like that to make it clear what it does. If you want to spawn off a big computation that could take hours that’d be a hugely useful way to isolate that computation from other mixed tasks that might be going on.