One should learn to hold altitude during a turn.
This means pulling back a little, and then pushing a little when one has levelled out (otherwise you will climb up a bit).
OCAS, perhaps no need for it but one should always aim to fly accurately. It's not hard and then when you need to do it you can do it. If you are flying at an intended 3000ft, say, and you drop down to 2700ft, and you let that go as 'OK' then why not let it go further?