Some things like updated electronics being more efficient could add depth. Sent in a CZ-6/6A conversion a few years back for repair.....repair tech asked me how old it was
.....there were parts in it they had never seen. (Improper tuning can affect depth drastically on any model-and Dave Johnson's comment about that is posted on this forum.)
It might be that it is better from being different in some situations. It has 4 tones, definitely better; but the enhanced mode is recommended for areas where you are finding older coins.
They widened some of the notches but not all to try to get some older good targets to fall in them-the downside is in areas with newer coins you will get more trash.
The "salt mode" does two things, it defaults the enhanced mode to standard notch such as a CZ-5; but there is a second purpose-it cuts down some on the 'front end' transmit power and makes it
more stable (recommended in wet salt, under some mineral conditions.)
You will have some objects bounce between two notches; depth can cause this as can target oxidation. In some situations (normal depth) you will learn that this bounce can only be one target-its worth learning.
Look for the Fisher Intelligence with NASA Tom it's online (and Tom may have it posted.)
Tom's site has articles posted on hunts/situations with various units; he will answer any question you put to him.