Okay...Well that the WaPo says so doesn't exactly make it be so, but it does suggest there's a better chance now than before now that it is so. Did Mueller or one of his team explicitly say that is the case? If so, well, then, it is indeed so.
If they leaked that information, whoever it is, Trump should fire them as they are no better than those they are allegedly investigating for leaks,
That's a different matter than whether Trump is under investigation for possible obstruction of justice.
I don't know the extent to which the general public has a need to know whether Trump is under investigation for possibly having obstructed justice. That is what it is, but as the information has been released, it's moot whether extant be the public's need to know that.
What I strongly believe is that many of the people -- without regard to their political affinity -- who will attempt to discount the significance of Trump's being under investigation for a felony are the same people who feel that if a liberal is under investigation for something, s/he is guilty of that for which they under investigation, and that's with regard to subjects who don't have a long track record of being shady, actually breaking laws, lying about things great and small, pretending to be someone they literally are not, etc. What will they think about this latest revelation?
I know what has always been my position in such situations, so I don't have a dissensus that compromises my integrity because of what I think about Trump as a result of his being investigated for possibly having committed a (or several) felony and what I think of others whom I knew to be under investigation for possibly having committed felonies. Of course, that only is so because I'm principled, not partisan.