[M T]

How about a different take?  

If the training of the pilots hasn't progressed to the point of their being effective (which I believe Goose has suggested), what would happen if Ukraine had the aircraft now?  They'd be under strong internal pressure to put them in the air, even if the pilots aren't ready.  If Russia picked off those 6 aircraft in short time, the effect on morale, as well as the combat effect, would be bad for Ukraine.

So, maybe, an external delay on the delivery of the aircraft may be what the top military people in Ukraine want.  Have the aircraft and the better trained pilots when the mud dries and Ukraine again tries to regain ground.

[M T]

How about a different take?  

If the training of the pilots hasn't progressed to the point of their being effective (which I believe Goose has suggested), what would happen if Ukraine had the aircraft now?  They'd be under strong internal pressure to put them in the air, even if the pilots aren't ready.  If Russia picked off those 6 aircraft in short time, the effect on morale, as well as the combat effect, would be bad for Ukraine.

So, maybe, an external delay on the delivery of the aircraft may be what the top military people in Ukraine want.  Have the aircraft and the better trained pilots when the mud dries and Ukraine again tries to regain ground.