Put differently (and, to my ear, more intuitively), time spent fixing bugs early has a high chance of being wasted because the part you fixed may not be needed after all.

Which is my experience, too, but then again I'm not writing software for space ships. I had the impression that space programs tend to be very well[1] planned in advance, and requirements change little once stuff actually starts to get built. (I'm saying this pretty much as an ignorant outsider, hoping to be corrected if I'm wrong.)

[1: Or at least meticulously, though looking at the apparent difficulty of the problems and the success rate I'd think "well" is deserved more often that in most endeavors.]