But you've missed the important point that the Jaguar cores were woefully underpowered in PC gaming terms. You don't need 8 cores on PC to match the power of the Jaguars. But the new consoles are Zen 2 based, which are light years ahead of Jaguar and superior to Intel's Skylake architecture (Comet Lake is still Skylake). So the advice of "8 PC cores because the next gen consoles are 8 cores" make perfect sense and will be very much the case in about a year once devs start wringing the necks of the consoles.
PS4 having 8 cores has zero to do with anything, the statement is "next gen consoles have 8 cores", not "previous gen consoles had 8 cores".
None of that follows, if the advice was to copy console core counts (as it was), should have been 8 since 2013. Anyway, I agree with the advice, because we see evidence that games are now utilising 8 cores and 8 core CPUs are now cost-effective, rather than basing it console core counts (which have been 8 since 2013).