It's certainly not as straightforward as cutting new lines. Recutting existing work often reveals mistakes that were made when the pattern was originally cut - you have a choice of recutting it as is, or sanding the lot off and starting again ( not ideal when you've already put a good few hours into refinishing the stock ) or trying to correct certain areas to balance it all.
Most of these 90's Custom Stock made stocks show definite bias to the master lines, rounded, unfinished line cuts and directional change in the pattern ( examples below ). This is when the operatives at CS started to use a powered hand chequering tool. That can be a bit of a pig to sort out but it's not impossible and certainly looks a great deal better when corrected.
https://i.ibb.co/pLj68Nx/IMG-2709.jpg
https://i.ibb.co/bdtRjNv/IMG-5362.jpg
https://i.ibb.co/GCNcDCS/IMG-5363.jpg
Recutting is also one of the best ways to blunt a tool due to all the grit and grime that's accumulated in the cuts over the years. I've started using home-made tools for this as I can sharpen them back up again - as opposed to ruining expensive imported tools.