ΔE 89.2, loose: different enough that you should pick on purpose. Chipping Medium is noticeably lighter than Matt Black Primer.
Can I use Chipping Medium instead of Matt Black Primer?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 89). Chipping Medium is noticeably lighter than Matt Black Primer.
Can I use Matt Black Primer instead of Chipping Medium?
The same difference applies the other way round: Matt Black Primer is noticeably darker.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.