The use of statistical terms to express devotion to an opinion has always bugged me.
Probability has mathematical meaning when a ratio of desired outcomes to the total range of possibilities can either be calculated a priori (rolling a “7”) or from repeated sampling (weather data). In these cases terms like “virtually certain” (>99% probability), “extremely likely” (>95%), “very likely” (>90%), and “likely” (>66%) have accepted statistical meaning.
In the context at hand, the tweeter is simply expressing an opinion of his own opinion.