This is true (I think -- I believe someone has produced a homozygous pinstripe) except that the problem is that only 1/3 of the pinstripe-appearing offspring will be homozygous, and you can't tell which ones until they grow up and breed!
So I can't really imagine wanting to do that breeding as 1/3 of your pinstripes are significantly more valuable than the other 2/3 ... But without knowing, you've just got to sell them all as "33% possible homozygous pinstripe," or what have you. (And if you were doing the breeding to hold one back, you've got a lot of work ahead of you proving the homozygous one out.)
As far as the OP's question -- my guess is that if anyone is/was working to breed the lethal factor out of the pearl, it was the originator of the morph themselves (ie, NERD). If the lethal factor is inherent in the "HG woma" gene itself, then it can't be bred out, as others have said -- just like the "wobble" or the (theoretical) homozygous lethal factor can't be bred out of the spiders, either.
If the lethal factor was just linked to the "HG woma" gene, then yes, after some outcrossing it could be bred out ... But if it is too tightly linked, that could be difficult to impossible, and if it was not all that closely linked, it probably would've been done by now.![]()