Unfortunately, it's not. In Mueller's letter, he states he doesn't support *Barr's summary of Mueller's conclusions* (for emphasis, *not* Barr's conclusions themselves) and then Mueller goes on to tacitly approve of Barr's conclusions by saying they weren't incorrect in their subsequent phone call. 

He's essentially lying by omission by not mentioning Mueller's objections to his characterizations but his actual statement isn't strictly false going by these reports. Barr will argue his conclusions refer to his decision not to indict on Obstruction which Mueller didn't comment on directly (unless we get more information) and not his overall characterization of the report which is what Mueller *did* object to.

Just weasely lawyer evasion which is more of what I expect we'll get tomorrow.