Obviously, this is a consequence of the fact that high ranking cards in an 4 cards Omaha hand contribute less to equity than in Hold'em.
Given the structure of the Omaha game, a significant contribution to equity comes from hands that have the potential to make a straight.
For example:
[AK][AK] hands will make a straight to the river in cases AKQJT and A2345. 2 cases.
[AT][AT] hands will make a straight to the river in cases AKQJT, KQJT9, QJT98, JT987, T9876, A2345. 6 cases!
The probability [AT][AT] hands will make a straight is much higher than [AK][AK] hands.
If you specify [AT][AT] and [AK][AK] in the program, we get the following result:
As you can see, values for oesd, gutshot, backdoor sd on the flop are higher [AT][AT] .