I don't believe that story at all. I don't believe that Stephany hit him either. Lies, lies, and more lies.
It's so unlikely that Stephany hit/slapped him (or touched him at all), the statistical probability is in the infinity range. Imagine you have very limited physical strength (especially little upper body strength) as compared to the very imposing figure whom you are alone with in a hotel room and you learn that this imposing figure (that you are alone with) is the number one suspect in the killing of another young woman when they were alone...
Do you:
a) Hit him
b) Verbally admonish him
c) Or otherwise anger him in anyway whatsoever
d) Be as agreeable as possible to anything/everything he says and does while devising an excuse to get away from him as soon as possible (go yourself for coffee, go with him to get coffee, you need a refill, you forgot something in your Jeep, whatever).
That is, the whole scenario that she learned who he was with respect to NH is likely just the fiction that JVS thought up to support a story that she hit him which provoked (legally, "provocation") a reaction.
JVS is undoubtedly familiar with homicide law (because of NH & his father's legal experience), and any provocation (vs. premeditated or felony murder, e.g., theft plus homicide) will reduce a sentence by half (voluntary manslaughter) in the U.S. & the Netherlands. Involuntary Manslaughter would never work since there was intent to kill her (suffocation), so provocation was his only mitigating option when choosing a statement to give authorities once they weren't buying the two extortionists story.
As a side note, I believe that the fact that he looked up ocean currents is informative. JVS is not an independent thinker (reinvent the wheel if the wheel even if it works just fine type of guy). Imagine, again, that if you want to get rid of a body, and you have done that before--with such a high level of success that you can actually walk around admitting your involvement with impunity--you will seek to duplicate those highly successful results using the same method (because other methods are unproven, and might result in getting caught). That is, this was likely what happened to NH, IMO, and it is unlikely that JVS came up with that plan on his own. Someone who had read many forensic files/criminal cases (like an attorney, e.g.) could hatch that plan in a split second, however.
It's also interesting that the story he settled with after a while (and surely after counsel from PVS) was that when he heard she was missing, he "hoped" she hadn't tried to go swimming (after leaving her on the beach), and also that she had wanted to go see sharks swimming. I think that was alibi-laying for if and/or when her remains (requiem en pace) were found in the ocean.
On a final note, for anyone who might believe that AVS is an innocent victim, it is extremely unlikely that, IF PVS got up in the middle of the night, perhaps printed off ocean currents, went out of the house for a few hours, came home, placed his clothing & JVS's, shoe(s) & all in a disposable bag of some sort, showered, etc., that he did so without her knowledge and complicity.
Or, even if PVS was not involved, that JVS didn't admit the truth to PVS & AVS at some point in time, meaning AVS would have knowledge and after-the-fact complicity. She, not JVS, is the one most likely to come clean now that PVS & JVS are "out of the picture," and I would think that NH's family realizes this as well. This may be the reason for NH's trip to Aruba at this time.
And while she may have kept silent out of fear for her own safety while PVS and/or JVS were still around, what she does and says now (or in the near future) will be telling of who she really is at heart, independent of PVS & JVS.