Just replacing my master cylinder

i bought the JB1196 (PBR Model) to suit 120y disc front drum rear with no booster (11/16th size)

I have 4 wheels discs though (hilux 4pot front, bluebird disc rear)

i knew about removing the check valve, so i pulled apart the two bottom sections of the cylinder with the intention or removing the check valve from the rear brake circuit (to suit rear disc)

out of curiosity i also opened the front circuit, and was surprised to see a check valve in there

can any one explain?

ATM im going to push on just removing the check valve from the rear circuit as has been advised but im a little confused by my finding