Well he did mention this
https://twitter.com/officialmcafee/status/943927015656316928That he doesn't hold any position in electroneum and so he is not pumping for any gains.
@Ashcoins
Shared workspace in bay area is common and another common thing here is starting a company in a garage

and so that doesn't make it a scam.
But truly how would you really know he doesn't hold any position in any of the altcoins he says or going to say are good. Honestly if he has that much of a influence he would be stupid not to be buying up the altcoin the day before he tweets it's good and taking profits from the pump.
You can't know if he holds or not,and that's the reason he probably does hold a position and he is using his status to gain profits illegaly.
I believe that he is either getting paid by a big whale or a developer or is holding a position, that's could be the only explanation to what he is doing.
In the crypto world, you can't really know whether someone is lying to you, and you can't really know if he is holding a position or he is just telling what he thinks in an innocent way, but always make your own research before investing in an altcoin and make sure that it hasn't gone up already.