The PDP-10 family ran a few operating systems in its life, some of which had better or worse user interfaces, but one of the things the all had in common was a focus on interactive use as opposed to batch operation or even block-mode terminals. Interactive use means each concurrent user represents more system load compared to the alternatives.

The pdp 10 was introduced in 1966. DOS/360 was introduced in 1964, prior to the PDP 10. Thus, there was nothing to borrow when JCL was invented.

Again, what examples of existing languages were available at the time the JCL was invented?