Do you need more to "pre-empt" with a major, than a minor suit?
Your statistical analysis is completely wrong:
 As a preempter, your shortness in unbid major(s) increases the likelihood of opponents having an eight-card major fit. This fit doesn't have to be their longest suit, and the hand will often play for more tricks if it isn't. As a matter of systemic agreement the opponents will often choose to play in an eight-card major fit regardless of other hand features, unless a running side suit with stoppers has been identified.

So no, no-one suggests that you need more to pre-empt in a major than in a minor (at the three level). That 3-level pre-empts in a major may typically be made on stronger hands than in a minor is because the top=end of minor preempts tend to open a Gambling 3NT instead.