Isn't it far more likely that expert advice from Russia was either:
a) how to wipe the data entirely (then can blame MH pilot for turning stuff off, with handy recent example of MH370).
or (even more likely)
b) that the data will tell no one anything about _who_ fired whatever took the plane down, so just hand the things over and make yourselves look good for once.
Infrequentflyer 789: Well yes, after all the Russian narrative is Ukraine regular forces fired the missile. The main point though here is that once evidence chain of custody becomes suspect, the evidence becomes suspect.