He is right as when we trigger Article 50, we have 2 years to negotiate an exit deal that is acceptable to all of the other 27 EU countries. The only realistic route is a half way house EEA deal as this will not involve any EU treaty changes. Any other route means treaty changes which have to be unanimously agreed and ratified by all 27 EU countries. This is realistically impossible in two years at the end of which with no agreement both sides go back to the default WTO tariff rules.
This is soft #Brexit far from ideal as it means we have to stay and pay into the single market and accept freedom of movement and constraints on other trade deals. In parallel to the EEA agreement we need to also be negotiating either a bespoke trade agreement with the EU or an EFTA one, which will give us our full fat (hard #Brexit) result. 4 years is a realistic timescale for this. There is 40 years of EU embedded legislation in UK law which needs to be unravelled in sensible ways to minimise disruption to UK trade.
Although this is not ideal, where the exit process is drawn out, the advantage is that it minimises the risks and disruption to UK/EU bilateral trade. I did highlight this and put up a link to the document and video that explains all of this by Dr Richard North with his Flexit proposal, during the referendum campaign, so to me it is hardly new news. For the terminally impatient Hard #Brexit in one 2 year move is possible, but does carry risks to UK/EU trade.