Hooves being too dry or too moist have nothing to do with the farrier and everything to do with the horse's living environment and diet
The hoof scar he got as a yearling from barbed wire is going to be with him for his entire life - there's nothing you can do about that.
I have a horse that also went thru a barbed wire fence, right after his previous owners bought him. Joker was 3 or 4 when the Boss Mare ran him thru the fence and ripped his chest, leg, hoof open.
He is now 12 years old. The hoof scar has never bothered him for shoeing, or to keep him barefoot. He is insulin resistant so he gets a soy-free vit/min supplement but no grain. He is one of those rare horses that is flax intolerant, so the only flax he gets is what's in the vit/min supplement. The other three get extra flax.
At any rate, just be sure to keep the trims current, according to how fast his hooves grow.
I noticed a surface crack below the scar tissue. That could be there for several reasons, including pressure from the scar because his toes are too long.
It's hard to see but the right front is the one with the old scar tissue, just like your horse has. Joker's is slightly right of dead center. I also learned, in 2010, that he is insulin resistant, so there's what the vet called "sub-clinical laminitis" still growing out in these pictures.
Point-being his hooves have had a lot to deal with; what he has in his favor is exceptionally thick hoof wall. If he ever gets surface cracks, I have messed up his trimming horribly. I hope this helps ease some of your concern but still keep an eye on the scar and don't be afraid to oil it if it looks like it might want to separate.
Regarding the frog sawing:) My computer screen skewes everything but I think the farrier may have taken off the amount he did because there was some thrush in the hoof. Do I see a purple dot of Thrush Buster on the frog or is that my screen deflecting colors again?
Another of my horses has a mild club hoof and deals with thrush every time the seasons change. I just got done shaving off the "soapy" dead stuff, along with as little of the live stuff I could get away with, that the dead stuff wouldn't let go of.
Again, it could be my screen and I'm not seeing things correctly. You are correct that frogs don't generally get trimmed but if there's fungus and/or bacterial growth sometimes a little of the healthy has to be cut to get all that's not healthy:)