It does seem that way, but if we look at Martin he does now have a well rounded game, and his tackling has improved, but probably is still not what youd expect from someone with his strength.
whether this could have been done without taking him too far to an outside game, as seemed to happen, who knows? Its not something I have had any real long term experience with, but I doubt a player will ever forget how to win inside ball.
Tackling accross the board could be better, but do we have any examples of someone who showed themselves to be a good tackler, in terms of numbers and technique, that has had this coached out of them?