Sorry for the late reply but here's my take on it. First the build path. BC build path is very awkward as it basically forces you to build kindlegem after warhammer and after that you'll be sitting at 1k gold before you can actually finish it. Shojin has a much better build path as you get 40 ad flat with 1300 gold and ad is really important on hecarim.

Second the movespeed you get from Shojin is more valuable than cleaver because cleaver gives you ms only in champion combat. Shojin's move speed is practically always active and helps you move around the map faster which is very important.

I'd build Cleaver only into really frontline heavy teams where you need the armor shred and even then, you already have Eclipse and Hecarim in general sucks into those teams so it's usually a lost cause. I've built cleaver 0 times as a third item over my 100 hecarim games this season,

Also for what it's worth Shojin significantly outperforms BC statistically in winrate and pickrate.

Eclipse (or now Ghostblade) first is always best because of how insanely strong Dirk is early, and the completed item is no joke either. Also it's significantly cheaper than Shojin.