It's always good to get some new knowledge and this thing came to my mind recently. Why some games need v-sync option to avoid screen tearing while others do not? For exempla recently i played Dark Forces 2 - Jedi Knight and although this game seems to not have v-sync setup there was no screen tearing. In next game from this series - Jedi Outcast I needed to=turn v sync in option cause tearing was quite drastic. Does it depend on game's graphic engine? Or maybe just JK1 had v sync turned on permanetly by default why JK2 did not?

For games nad computers that don't use adaptive sync, the higher the frame rate and screen refresh rate are, the less tearing you will notice. Higher framerate means that the previous calculated picture is a lot more simiar to the current one than when the framerate is low. Higher monitor frequency means that there may be tearing, but it's visible for a shorter time and maybe not noticeable at all.

Jedi Knight is ancient, it was built for Pentium machines from 60 to ~200 MHz and can even run without graphic accelerator, the possible framerate is extremely high so you may just not notice the tearing.

Also the drawing method could make a difference. JK uses directdraw to bring the calculated picture to the screen, while JO is built on the Quake 3 engine using OpenGL. On modern computers the ddraw dll for JK has to be replaced with a more compatible version, some would call it an emulation. I don't know how this dll handles different frames.