I think 90% is WAY too high of a number. Even if it happens only 20% of the time, that is pretty significant if it is unknown or mostly unknown in other morphs.
Consider this, if you have a co-dom morph male, and you pair him to a normal female. Hatchlings of this morph sell for $250 (for simplicity, I'm going to ignore any price difference between males and females). If the female gives you a big clutch of 10 eggs (or you can think 2 females, 5 eggs each, if you prefer), you can expect about 5 morph babies, or $1250. However, even if only 20% of the hatchlings are defective, that reduces your expected sales to $1000. That's significant!
Let's use 80%, which would still be "not defective" based on your number. So, out of those 10 eggs, you can expect only 1 healthy morph hatchling. That's "ok" with you?