Yes it's massive for Campbell and a huge event having the P4P king fighting in the UK.
I don't see this as a mismatch at all,

Campbell is the UKs best ever Amateur by far -

Luke Campbell, MBE (born 27 September 1987) is a British professional boxer. He held the WBC Silver and Commonwealth lightweight titles from 2016 to 2017, and has challenged once for the WBA and Ring magazine lightweight titles in 2017. As an amateur, Campbell won gold at the 2008 European Championships and 2012 Olympics, and silver at the 2011 World Championships, all in the bantamweight division.

Not saying he'll win but I think he'll do better than people think.