Does cutting a root cause it to die?

[plantluvver]

I am reporting some Oncidium (Intergenerics?). I watched some videos on YouTube, but I still cannot always tell if a root is bad. I now realize that I beleive that cutting an orchids roots will cause the root to die, that a root cannot be healthy without a growing tip.

Does killing the tip cause the root to die?

I have attached photos. There are "three" different plants. (The first I worked on seemed to be actually two once I got the roots untangled.) I used a different background for each plant.

I have yet to read up on rescuing a an Oncidium with no roots.