Its worth noting the CAPA article is by no means affiliated to Hainan, and is just expanding on already reported info with its own opinion. Therefore, just because they say 'its difficult to see a MAN flight', does not mean that view is shared by the airline.
Its also worth noting that Hainan have not applied for LHR slots. The table of 'future routes' by Hainan, being quoted by various sources lists purely 'London', to which STN and LGW were the 2 airports vying for the service (Richard Maslen of routes picked up on HU looking at STN a few months ago in fact). LHR was purely a translation error by someone on a.net (to which they corrected to say just 'London'), but for some reason LHR seems to have been continued to be broadcast.