Said that the flairs help the sole be larger and touch more of the ground, which is needed for pulling. That the sole is what they stand on and what they need to use to move loads.
Flaring - that is, allowing the walls to distort away from the internal foot actually causes soles to 'drop' and become thinner. For soles to remain thick and therefore able to provide adequate support & protection under the pedal bone, walls must also be tight & strong. And flaring may *look* like it makes the sole bigger, but the true sole stays only under the pedal bone. What becomes larger, 'stretching' with the walls is AKA 'lamellar wedge' material.
As for soles needing to be flatter & larger(than what the internal foot/anatomy dictates) for heavy loads, I don't get the reasoning of that idea at all. On soft ground, they need to be able to dig their toes in, and on hard surfaces, it only delays breakover, effectively making it harder on the horses - more musclework for each & every step! Aside from the bad mechanics acting against hooves & joints.
any big heavy horse is more prone to flatter feet. I had a foundation quarter mare, she was short stocky bull dog type and had terribly flat feet. To make her not flat footed would have been to tamper with the natural foot angle , letting her heel grow to a higher than normal length.
I do agree a lot of farriers are fast with drafts feet, simply because the horses are so heavy, it is difficult to hold up that hoof. The drafts I have and kept here, would only stand 3 legged for a short time.
Yes, heavy horses, or weak footed horses - TB racehorses for eg, who very often have rather laminitic feet - are indeed 'prone' to flat feet *if not managed carefully*. Of course, every horse is individual, some naturally have less concavity than others, but I'm assuming that's not what we're discussing here, but we're talking about flared, stretched, 'pancake flat' feet. Therefore I will disagree that improving flat feet would be detrimental to 'angles', such as require high heels. As with any horse, growing out flares/flat feet requires walls to be quite short all round, in relation to the sole plane to reduce the pressure on them, allow them to grow straight & strong. And allowing the soles to a certain degree & frog to *comfortably* bear the load. Once that happens, the soles can begin to thicken too.
I think it's not so much the weight of the animal/leg - if they're well trained, that may be negligible. And you usually don't have to bend far either, which helps! Give me a well mannered clydie any day over an obstreperous pony. But more about the behaviour of a lot of drafts - they may have had less good training, or learned to use their strength against anything annoying like farriery. And too many farriers IME are of the belief brute strength & bull attitude wins the day with horses... not that I could pull that off if I wanted to... And the fact that on a draft there's usually so much more HARD hoof to trim, than normal.
A well mannered but arthritic draft... definitely need the hoof stand! So many horses I see are also difficult to trim because they're sore, or *can't* do as the farrier may want. They may not want to lift one leg, can't hold them up for long, can't lift them high, or out to the side... whatever. That's still hard on you, regardless the size of the horse... unless it's a pony small & safe enough to sit down beside it to do!
I will take the time on a horse that is sore, to do the job as well as possible & ensure he has a reasonable experience too... even though this might include me trimming in... yoga poses for some sore horses! If their 'behaviour' is just down to lack of training/manners, then I'm happy to spend time training too, if you pay me for it, but don't expect me to put myself further in harm's way to just get the job done. Farriery doesn't pay that
well & I only seem to have one body.