There's a big long nerdy blog post about it (where I learned this technique) but basically many tools will throw away information and take you back to the start of a tricky merge. With the right settings, you can leave all the easy bits done and see exactly what caused the problem.

I think the guy was campaigning to make it the default so it may be in some tools now.

I'll see if I can Google it up.

edit, think this is it:

https://www.eseth.org/2020/mergetools.html