Bo are often wielded two handed like a spear, using similar thrust motions. Then there’s the two-ended techniques that strike with both ends of the weapon. Spear and staff techniques overlap in many regards (2012 series shows Donnie added a concealed blade to his staff, making it a polearm-like/naginata weapon).
Sai doesn’t disarm sword, at least not reliably, since the katana is also usually two handed weapon, plus Leo dual wields just like Raph and Mikey.
i say they are two diff weapons because a bo reaches the bridge of your nose and a spear is longer than you. basic strikes overlap but outside of that its very different. bo isnt really big on thrust techniques do to its a blunt object…its power comes from striking at the angles. https://en.wikipedia.org/wiki/Sōjutsu