Why is the stroke order of 牛 different from the 牛 radical in 物? According to Jisho, the 3rd and 4th strokes of {} are written with the horizontal stroke first, while for {}, the vertical stroke goes first: ![stroke order of ]( vs ![stroke order of ]( This does not seem logical to me. Is there any historical reason why this is the case?

Easier order to start next stroke is chosen there.

Writing letters top-down (and right-to-left) has long been the only way for Japanese until late 18th century (Wikipedia). Try following that way and you'll feel the difference in order reasonable. If you use a writing brush, it'll be more convincing.