I have hunted in soil that is considered very mild to dirt that is a bit more mineralized to soil all the way up to what I hunt in now which we call devil dirt for a reason.
I have used several detectors, some with ground balance and some without and have been successful with all of them...everywhere.
Can GB be advantageous, of course, for optimum hunting in problem dirt for sure but in mild dirt I don't believe it so much.
It will range from hardly any difference at all to maybe a slight difference but a huge difference, don't think so, not in my experience.
The proof is in the numbers.
One of the biggest sellers of all time has been the Ace 250, a unit that helped bring this hobby to the masses because of the low price and had no GB feature.
Literally hundreds of posts from owners that started with this one that found plenty of treasure over the years despite lacking that and in areas of milder soil they could go deep and find targets without ID problems at all.
I have much experience with an F2 as have many others that have seen the same and in decent soil depth never seemed to be much of a problem and no GB on that one either.
I read many forums and posts about Tesoros too, can't tell you how many have been surprised on the depth they got using some of their units without and GB adjustability...especially the Cibola which can be shockingly deep in good soil without it.
To get the deepest, best ID's the standard smaller coils work well but adding a larger coil to the mix seemed to help.
I have read a huge amount of posts from hunters reaching the 8-10" area and even sometimes further in many areas of the country using both standard and especially good size coils on units lacking GB adjustability like 250's, F2's, Euro Tek Pros and more...even though the bulk of the targets most of us find don't seem to be much deeper than the 6" depth area.
Not all but most.
If these types of lower end machines were so bad at this that they could not ID targets decently in any kind of dirt they would never have sold units in the numbers they have over the years and owners would not have talked about them so positively as they have done.
They all do have GB capabilities, even the cheaper ones, it is just that many are pre-set at a specific area by the factories which is in area that they choose to and assume will work the most optimally in the largest amount of states possible and in my mind that would lean to the milder stuff.
More expensive units added adjustability of this feature and many modern lower price units have started to do this also.
Will units without it be useless in a large part of the country...hardly.
In the difficult areas will it help and a lot...sometimes.
In my extremely difficult dirt I usually opt for units that have it to get the deepest with the best ID's and data to give me a shot at the most targets possible but I also have used and still use a couple with a pre-set GB from time to time and you know what...still find plenty.
Maybe not as deep as my primes, maybe not as optimum in the data I can get as my upper end units that were much more expensive but did have more features but they still work, I still have a blast using them and they still find metal...sometimes some shockingly great metal.
When I hunted in mild dirt I never worried about it, if I did I wouldn't have used that F2 or a Compadre for literally hundreds of hours and found so much...I would have opted for manual GB units right away and never looked at the ones without but this was not the case...probably 90% or more of what I found in dirt like yours could have been found with any of them.
I started hunting in the horrible stuff with units without GB, still found plenty and never worried about what I couldn't find.
Moved back to it after 3 years hunting in heavenly soil and learned that GB does help me some but still don't worry about it and still pull out units without it from time to time and still manage to find treasure.
This is my opinion to the answer to your question about GB capabilities in mild dirt...
Is GB a must have in every situation...not really, especially in milder soil.
It is nice to have, recommended if you can get it for hunting everywhere for the most optimal hunting possible but will it make such a huge difference in the mild stuff you need to worry about it if you don't have it...no.
If it was there would have been a huge amount of lower end and even higher end units without it that would have never been sold, used or enjoyed by the masses.
You can still find treasure and get great data even on deeper targets without it if you are lucky enough to live in parts of the country with better dirt.
Not everyone has had the experience of hunting in soil that ranges from heaven to hell...but I have.
A car without air conditioning or an automatic transmission will drive you to your destination just as a car without them can...both features are nice to have but absolutely necessary for all situations, I don't think so.
So say the numbers and logic.