The sentence in bold is/was an attempt at a bit of humor, Ms Tan. I'd say that there are lots of idioms that don't reach the status of a proverb. There were some good ideas presented here as to the differences.
The only real difference that I can think of right now is that a proverb seems to carry a message.
The idioms, 'kick the bucket' & 'buy the farm' both hold the meaning 'die' but they convey no "deep" message/meaning. They are not proverbs. I suppose a proverb could be an idiom but not all idioms are proverbs.
Look at it this way. We all got this far in life without knowing the difference, at least consciously, [and I can assure you that it's pretty far for a lot of these jokers] and we haven't suffered a great deal.