Well, Korean Air has a lot of restrictions on Delta tickets -- most lower tier fare classes earn ZERO miles...
here is the table from AeroMexico - where I believe Delta OWNS a chunk of this airline:
Premier Kilometers’ accrual chart
Cabin
Fare class
Base KmP
Bonus
First Class
F, A, P, G
100%
50%
Business
J, C, D, I, Z
100%
50%
Coach
Y, B, M,
S, H, Q, K, L, U, T
100%
0%
Coach
X, V, E 75% 0%