1) Molly no longer has a flare in the lateral quarter/toe
2) her whole hoof capsule is smooth, without ridge
3) she lands flat with such an alignment whereas when the lateral side would be higer, she hits her toe prematurely.
Actually, base narrow horses are rather common. Gene Ovnicek made a small movie on pigeon-toed (base narrow) horses:
where he points out that most older feral horses he studied in the wild develop pigeon-toed (base narrow) status as they become heavier and need to to support their massive body weight.
I realized that this bison of the Black Hills, South Dakota, roaming freely, also positions his legs such that he can support his weight best UNDER the body. This suggest to me that base narrow status is rather the norm than the exception for heavy-bodied animals.
The problem comes in when people try and straighten those horses out that are base narrow. Or do not know how best to support their base narrow conformation with their hooves, when hooves in domesticated setting do not receive enough wear so that they can themselves conform to the horses conformation.
The thing that is important to realize with base narrow horses is that they tend to slightly overload their lateral sides of their hooves.