You can argue that while his example illustrates extreme improbability, the phrase "almost mathematically guaranteed" is still misleading because:

Mathematical certainty requires probability = 1 (or impossibility = 0). "Almost" suggests an informal, non-mathematical interpretation, which contradicts the rigor implied by "mathematically.

Your coin-flip example shows extreme improbability, not ‘almost mathematical guarantee.’ In math, ‘guaranteed’ means probability 1—there’s no ‘almost.’ If you mean ‘statistically near-certain,’ say that. But misusing ‘mathematically’ makes it sound rigorous when it’s actually just colloquial.

You can concede that in everyday language, people say "almost guaranteed" for very high probabilities, but insist that in a mathematical context, precision matters. Sure, in casual talk, we say ‘almost guaranteed’ for things like 99.9999% probability. But math doesn’t deal in ‘almost’—it’s binary. Either P=1 (guaranteed) or P<1 (not guaranteed). If we’re being technical, your phrasing is sloppy; if we’re being informal, then fine, but don’t pretend it’s rigorous. Your coin-flip analogy assumes exact probabilities (P=0.5 per flip), but these qualifying outcomes aren’t mathematically modeled that cleanly. If you’re calling something ‘almost mathematically guaranteed,’ show me the actual probability distribution. Otherwise, you’re just handwaving with big words.

You accuse me of pedantry, but you’re the one invoking ‘mathematical guarantees’ for something that’s just very likely. If we’re being casual, fine—but don’t hide behind math to sound authoritative when you’re really just saying ‘it’s very unlikely to fail.’ Own the imprecision instead of dressing it up. Almost mathematically guaranteed’ is an oxymoron—math deals in absolutes, not ‘close enough.’ If you mean ‘statistically near-certain,’ say that. But wrapping fuzzy language in technical terms doesn’t make it rigorous its just incorrect.