More depth? Yes, depending on site conditions, soil type, and depth of coins.
Does IM -16 magically increase the transmit strength? Nope! The Explorer transmits at 100% power at all times regardless of any of your settings e.g. sensitivity, gain, IM, etc. Therefore the best possible signal you can receive on a target is in the control box waiting for you. Call this "gross depth".
You can then control depth via gain, sensitivity, iron mask, etc. You can eliminate certain signals (discrimination), filter weaker signals (sensitivity) and after that boost the fainter signals that are left in volume (gain). Via your settings you control "net realised depth".
If you decrease your sensitivity to 1 you will lose a lot of depth and miss targets. If you decrease your gain to 1 again you will lose depth on deeper targets and miss them. Isn't it reasonable then that discrimination could also adversely effect depth?
This depends on site conditions and target depth. In our local soils with the stock coil dimes and small cents start to sound pretty iffy at 7-8 inches. At 9 to 10 inches they can sound like crap. Now toss in some 200 year old rusty square nails at the same depth and discrimination becomes very important.
I have tested some deep targets that were quite iffy but nevertheless there in IM -16. I turned the IM up to -12 and they vanished, the iffy signal went 90% null 10% broken iron tone and the coin was gone. On occasion the reverse is true so its not 100%.
I'm willing to put up with all the iron noise in IM -16 because our deepest, most iffy signals are also generally the oldest most desirable coins. I may only dig one per hunt but its worth it. A half dozen 1900's indians, well that was exciting about 600 indians ago but a single 3 cent silver or an early indian that makes my day.
The second situation where IM can be an advantage is not so much depth related as it is improved target separation in iron. Again in our area with coins deep and lots of rusty square nails, most of the good targets that are left these days are hiding in the iron. Thats why they are still there after people have pounded these sites for the last 30 years.
In IM -16 I can often hear both the coin and the iron mixed together. Discriminate out the iron and poof the coin can vanish. Not always but often on these deepest, iffy targets. Our rusty square nails pollute a wide area. Its tough enough to get in close in IM -16, discriminating out the iron makes it all the more difficult.
The same target separation advantage applies to shallow modern trash polluting an area and overshadowing a deep nearby coin. With out the stretchy null getting in the way its often possible to hear both the shallow trash and the coin mixed together inbetween the two targets. I have to say those are my favorite ones to dig, there's nothing like digging the trash out of the way and then hearing the coin you thought was hiding there and going home with one many others had missed in the past.
I want to make the point that IM at -16 is beneficial mostly for those really deep iffy signals. Its not much of a help for an average 6 inch deep barber dime. If you don't have a lot of iron and your coins are not that deep, then there's nothing wrong with cranking up the IM and enjoying some peaceful silence versus all the low iron noise.
Now hunting an iron infested trash heap of a 1700's cellar hole is quite different. If there is a carpet of iron nails then running IM at -16 can be counter productive as the iron seems to overpower any other signals if you accept it. Discriminating out the iron via IM -15 or -14 scan be more successful in that type of condition.
Anyway those are my observations.