Did Percival Graves already know that this character was an Obscurial when he taunted them about being a squib?

Question

Towards the end of Fantastic Beasts and Where to Find Them there is a scene where Percival Graves, having previously pretended to befriend Credence Barebone with the promise of giving him magical teaching, apparently finds out that Credence is nothing but a squib and says that he is done with him. Seconds later Credence reveals himself as an Obscurial and transforms into an Obscurus. Seeing that he must be a powerful wizard after all, Graves then quickly but unsuccessfully reverts to trying to persuade Credence to accept him as a mentor.

While it is understandable that Graves would lose interest in Credence once the latter seemed no longer to be of use to him, his decision to taunt Credence with being a squib seems surprisingly imprudent. Even if Credence had truly been a squib, publicly dumping him like that converted a loyal henchman into an enemy just when Graves was most likely to need help. In other respects Graves showed a self-disciplined ability to stick to a role.

There would seem to be two most likely explanations for Graves taunting Credence. The first possibility is that because

Graves is really Gellert Grindelwald, his fanatical hatred of all who fail to be proper wizards overcame his common sense.

The second possibility is that he already knew that Credence was an Obscurial and taunted him with being a squib with the specific purpose of of provoking him to transform. That would be in line with his intention of provoking war between the wizards and the No-maj world. On the other hand, it would be a very dangerous strategy to infuriate someone who must be a very powerful wizard to have survived for so long as an Obscurial.

So did Graves know that Credence was the Obscurial before Credence showed himself, or not?

Answer 1

No, he didn't

In the official screenplay, Graves' taunting occurs in scene 96. In scene 94, just before Credence and Graves apparate to the tenement house (where the taunting occurs), Graves still thinks the Obscurial is female:

FOCUS ON CREDENCE, cowering at the back of the church, whimpering and clutching his pendant of the Deathly Hallows. Graves steps quickly toward him, bends down, cradling Credence’s head. However, there’s little tenderness to his voice as he speaks:

Graves: The Obscurial — was here? Where did she go?

^{Fantastic Beasts and Where to Find Them: The Official Screenplay}

In fact, this is the reason Graves is so cruel to Credence: not that he's trying to provoke Credence, but because he believes has no further use for him; as far as Graves knows, the Obscurial is in the very next room.

Graves: Where is she?

Credence looks down — at a loss.

Credence: I don't know.

Graves becomes increasingly impatient — he's so close to his goal. He marches forward into one of the rooms

Graves: (contemptuous) You’re a Squib, Credence. I could smell it off you the minute I met you.

[...]

Graves: I'm done with you.

^{Fantastic Beasts and Where to Find Them: The Official Screenplay}

In fact, it's telling what goes through Graves' mind when Credence does start to reveal himself:

As each wall collapses in front of him, he is transfixed, elated, yet also aware that he has made a colossal error...

^{Fantastic Beasts and Where to Find Them: The Official Screenplay}

Answer 2

Yes, he did

Cheylianie: What did Graves-Grindelwald mean when he said "My vision only showed the child's immense power?" Is he a seer or was he lying?

J.K. Rowling: He is a Seer AND he was lying.

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