I would say there are two kinds of "Amazon lawyer" companies. One that has contacts within Amazon to get things changed - whether they should be or not. Rare and likely expensive.

The other much more common one has a number of appeal templates where they essentially replace a seller's name each time it's used. They are basically proof that a well written appeal gets results.That's what the company you mentioned do - all they do is write your appeal and then you have to submit it in the usual way.

Personally i think most sellers could succeed on their own if they took an objective look at what happened and structure their appeal how Amazon want it.

Avoid massive claims about having a legal department and an IT dept and a HR dept which are now all fully trained, avoid blaming Dave who they've now fired and just set out why things went wrong, what remedial action has been taken, preventative steps taken etc.