John Osterhout is a creator of Tcl, which embraces event-driven model for programming. I think it gives more perspective into his opinion.

That said, Tcl was one of the first scripting languages which got very nice thread model - see AOLServer [1].

[1] https://en.wikipedia.org/wiki/AOLserver

We used Tcl threads in one of our programs to control various hardware things while main UI responded to events sent from the threads. Everything worked very well, especially for a program in scripting language like Tcl.