I'm pretty certain they just advise you to take a level 1 course because you only need so many credits at level 2 so there's no point doing a harder course if you don't HAVE to.
Because Physics 2 is a 60 credit course I basically HAD to do 120 level 2 credits, whereas a lot of science students just do ExCos in 2nd year because it's really easy and thus lets them focus on the subject they actually want to do