These arguments are evidence-based (as opposed to formal logic arguments), so the use of the word “probably” is consistent with the limitations on certainty that inductive reasoning has. The right answers on these questions involve new pieces of evidence that generally help or hurt the argument without actual “proving” or “disproving” it. It’s a good observation you’ve made – the LSAT, and in particular the LR section, is largely about recognizing patterns and familiarizing yourself with structures – but I don’t think the use of the word “probably” is going to be much help as far as suggesting particular answer choices.