hfe > 100 is an assumption for our design. That does not mean every device of the same type will conform to that. Anyways for diy use we can hand select devices to suit our needs but then repeatability will be a bit harder.
It's easier to buy transistors of the desired A/B/C range and layout for the minimum gain. In practice it's sufficient to have the highest gain class in stock. A proper layout for hfe=50 will work with 250 as well.
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