In a sense, yes he changed the style however the old defence drilling will still there in his first season. The difference you can tell in the defence setup between his 1st and 2nd/3rd season was huge. This was down to him putting more of his idea to the team after the first season like not practicing setpieces etc.
Not denying his first season was a success by the way.
Again, not being argumentative for the sake of it but there is more to it than that.
He comes in and has a secure, fit and firing back 5 (inc the GK).
He has them split, playing out from the back with GazBaz slotting in. The full-backs become wingers.
There is nothing about that setup that is Moyes. Zero.
Second season he has Distin become an amateur footballer. Alcaraz cannot get fit (poor signing, definitely). John Stones has to then be thrust into the team. Baines also had a few issues that year which disrupted him - remember Garbutt made a few signings. Coleman also missed a few games.
So we've gone from having a secure back line, consistently playing to a backline completely disrupted. He can't drop Howard because he hopes that he will recover the form he was showing the year before.
He's also splashed his entire kitty on Lukaku. Any why wouldn't you?
The set pieces thing, absolutely. You're spot on. But to say the second season was because he had stamped more on the team is just not true imo. How could he change things to the degree he did
without stamping all of his ideas on the team.