yes, it is becoming an increasingly used tactic..
Breed from very high risk blood lines, then farm out the breeding cats to pet homes at 2 years old before they are likely to screen positive for HCM.
Breeder can then truthfully claim they scan for HCM, but at the same time know full well there is a very small chance they will ever have a positive screen despite using high risk lines.
The bargain price might not be so attractive IF you end up with a HCM cat 2 years later
Not saying this IS the case, they may be telling you the truth - stranger things have happened - and even if they are not it does not mean the cat definitely will have HCM, but it is a risk to consider.
Oh, and you will be faced with exactly the same dilemma with a full price kitten unless you are very careful where you buy from.
Personally I would be much happier to home an ex breeding cat which is 5 or 6 years old than one which is 2 years old