Of course he is still holding them and it is impossible for a developer to be a person who lose access to his wallet. This is impossible, a developer knows very well that he should keep a lot of backups of wallet.dat from his Bitcoin Core wallet in different places. Beside this it is in his own right to hold any amount of bitcoin he may have mined, bought or trade. That's the beauty of bitcoin , is fully decentralized and we should not care if someone is holding bitcoin or not, its none of our business.
Yup! even though he is saying that he already dump all of his bitcoin I also think he is keeping a backup of it and wants other people to do the same thing to dump their bitcoin so he can proceed with his scheme I think he wants to control the movement of bitcoin by giving FUD on the past, well I don't really think that is his real intention by we can never know for sure, he can always have his bitcoin by buying it, mining, trading he can do it in secrecy and nobody can ever notice it because yup bitcoin is anonymous and decentralized.