True.
If there is no regard for consistency, you may (or may not) get hybrid vigor, but you can't do so dependably.
Just because there is a "cross" doesn't mean anything meaningful will obtain as far as "vigor" goes. Some of the lamest bums I have ever seen were "straight crosses"
Some of the best, strongest, most intelligent, and most intense animals I have ever seen have been INbred ... on the right dogs
If you inbreed on the right dogs, you will not need a cross
True, some outcrosses just "click" ... and they work well in high-percentage ... and when "that" happens, you have the makings of a whole new potential bloodline and breeding effort
The only way to tell if a dog can produce is to breed it ... and to breed it enough different ways to see if there is a pattern and dependable prepotency that can be established ... which means the young have to be allowed to mature and be evaluated. This process can take up to 5 years to bloom, and many people make their decisions too quickly, either way, based on just the first few pups. Only enough variety, and the light of Time's perspective, can say for sure.
I hear this all the time and, well, if breeding is "just a gamble" ... then scatterbreeding is playing with an unknown deck in someone else's house ... while linebreeding on the right dogs is stacking your own deck and counting your own cards in familiar territory
Jack