I don't think that we need to know the average prime gap for this.
Assume that there are only a finite number of strong primes.
Then after some point for all triplets of consecutive primes p1, p2, p3, we must have p2-p1 <= p3-p2. In other words, the gap between consecutive primes must be non-decreasing after some point.
But since there are arbitrarily large runs of non-primes (e.g., [n!+2, n!+n] is a run of n-1 consecutive non-primes), non-decreasing gaps contradicts the theorem that there are an infinite number of gaps < 400.
Assume that there are only a finite number of strong primes.
Then after some point for all triplets of consecutive primes p1, p2, p3, we must have p2-p1 <= p3-p2. In other words, the gap between consecutive primes must be non-decreasing after some point.
But since there are arbitrarily large runs of non-primes (e.g., [n!+2, n!+n] is a run of n-1 consecutive non-primes), non-decreasing gaps contradicts the theorem that there are an infinite number of gaps < 400.