This was true at the time, but at the time Linux wasn't preemptive, had bad SMP support and no good threading implementation.

BeOS was designed for SMP hardware, was preemptive and had good threading support, but besides that there is nothing really especial about it. "pervasive multithreading" simply consisted in using threads a lot (for 90's definition of "lot"). Creating and managing the threads by hand. In 90's C++.

Modern operating systems have caught with that and gone beyond of what beos did.