"If he is eating, he is probably hungry."
Translation:אם הוא אוכל, אז סביר להניח שהוא רעב.
No. It is in fact not entirely correct, formally. אז should only refer to time description. But in everyday conversation we use it a lot, incorrectly, as the "then" component in "if-then". You could quite correctly say אם הוא אוכל, סביר להניח שהוא רעב, it would also sound ok conversationally, not too formal.
The second clause of the Hebrew answer is something I would think to translate into English as "then it is probable that he is hungry." That feels different to my ear (as a native English speaker) from "he is probably hungry." Can you comment? (And I've read the earlier discussion about whether אז is needed, so no need to comment on that aspect.)
I'm not sure how it works... I agree about your first statement, and it sounds like a longer way to say it; I wonder if there exists a shorter, more direct way to say the same thing?