I think I understand what you're saying -- but if someone is breeding for appaloosas, I would expect that one of the horses they use for breeding to be a visual appaloosa -- or why call it breeding for appaloosas? Just like in a pinto breeding program, you would normally be including a visual pinto in any breeding program. So if you're saying people would buy a 'visual solid' appy and breed it to another 'solid' and expect an appaloosa to result -- I would say they do not have an appaloosa breeding program, and they shouldn't be confused on why they didn't get an appy foal.
As to your friend, I think that's very sad, because the non-characteristic mare would have produced an appy foal since the sire was a fewspot and is therefore homozygous for appy and any resulting foal would have inherited an appy gene from the sire. I believe that chances are that "visual solid" was carrying the appy genes, even if not visual. If her stallion was truly a fewspot, then she really had no worries, since there are those with 0% patterning on the Appaloosa site that are still carrying the appy genes. Then, to cross to a fewspot, she would have been almost 'guaranteed' an appaloosa foal. Now, how she could expect to 'breed for' fewspots or snowcaps -- well, we all know that 'breeding' for those is a crap shoot.
Here's my solid mare (from Timberview), and her offspring when bred to different leopard stallions:
I have several "solid" mares here that produce color/patterning when bred to leopards or fewspots. My last fewspot filly was born from a leopard stallion and a mare with few characteristics, who as she matured developed minimal spotting on her rump. Spotty as a leopard stallion has produced both snowcaps and fewspots, which 'we' would expect since fewspots need a leopard or another fewspot to be in the mix of parents.
But once I purchased a full leopard mare, bred to a full leopard stallion and the resulting foal had no characteristics or patterning at birth. I would have expected him to perhaps 'spot out' if he had lived to maturity, but there are no guarantees. But you know how often those "solid" appies wind up snowflake appaloosas, varnish appaloosas, or develop spots on their rumps -- but heck, that can also take 7 + years to happen.
Like we all say, breeding appaloosa is a crap-shoot as to what you will ultimately see when a foal is born. And until the tests become available, and more is known about how some of the pinto genes affect the appaloosa ones, and the suppression of certain genes and tests for all, I just think it's fun to "see what you get!"
And then see the next year when you clip what's been developing under that winter coat....and the next clipping, and the next! Almost a new horse every year without having to spend any $$
.