That is NOT whataboutism.
It's really sad how people want to change the very meaning of words simply to justify their beliefs.
Whataboutism is justifying a behavior by pointing to another person that did the exact same thing, using hypocrisy to somehow make a point.
From the google definition, it's a tactic used by totalitarian regimes to justify their behavior by pointing at the same or similar behavior of their enemies.
For example, look at how Discipulous used a whataboutism in this thread to justify the left trashing the office of the presidency by showing an instance where the right trashed the presidency.
It's an appeal to justify bad behavior and it just does not work in a rational dialogue. Both parties can be wrong. It's not a justification.
Whataboutism totally does not apply to Trump in this case, since Obama did not do anything of the sort of what Trump did, so there is no attempt to use Obama's actions to justify Trump's.
To explain the circumstances of a situation by bringing up a prior president's policies is completely with merit on its own. To dismiss the discussion on the basis of "whataboutism" is exactly the same as charging a person with "racism." It's a baseless charge using a word devoid of its original meaning and used to shoot the messenger so you don't have to deal with the message.
That kind of insane partisan censorship is what is killing rational discourse today. These discussions should not be made taboo just because it makes one feel bad to think about it.