What do roots do? They acquire nutrients for the plant.
Why then would a plant need extra roots? = To acquire more nutrients; because the plant is not getting enough, or the plant has no more room for the roots to grow under the gravel bed .
I have always been a firm believer that "Proper" root growth comes from having "ALL" the nutrients in the gravel the plant will need throughout its life.
??? Do you fertilize in liquid or dry? Do you use plant-tab type? This is where the topic gets hairy(extra roots) My stem plants do not grow extra roots above gravel level, and quite frankly I couldn't care less if they did. They are thriving without change and have for years. I have not the foggiest idea why this is, but in my tanks it just does not happen. (I do use liquid ferts and root-tab type)
So...Do your plants thrive? If so maybe you could concentrate on the above fertilizer idea to find a reasonable answer to your quandary.
Since you've got different ideas in the other threads you've read obviously no "one" answer is correct. Quite situational probably. Try different ideas out to find the one that you find acceptable.
Lastly to get rid of the roots use the scissors and a little time to trim.
"You Killed Fritz!"
Bakshi references are always cool!