It's always a little riskier because if you build it in the middle of nowhere, you could be harassed, especially with Sipahi coming in.

Without knights, it's tough for Rus to play full infantry against the might of Ottomans when they have Sipahi with archers and Mehter to round out the composition and make it really potent.

Akinji destroy horse archers. They absolutely melt them even with Boyar's Fortitude.

Building knights against Ottomans doesn't feel best on King of the Hill. Ottomans are arguably the best anti-cav civilization, and cav is not something you want when it comes down to the center fight.