First things first in that the Zero LE Mk4.0 does not have the facility for an on-board phono stage. Next, Neither the Zero LE 3.0 nor 3.1 can have that facility retro-fitted. The option had to be ordered at the time because the version with it had a different main board (with the phono stage built in) compared to one that didnt i.e 2 types of main board. And no, on the other inputs there was no difference between a 3.0 / 3.1 with the mm/mc fitted and one that didnt.
