No, Marcus does not say he personally created Section 31 but he does appear to have high level involvement (likely the latest in a line of past and future Admirals who will be attached to it) so I don't see anything in the film to remove ENT's mention of it.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist