Is it true that all proverbs are poetic and figurative in nature?

No. Not all proverbs are poetic and figurative in nature. While many proverbs do employ poetic devices and figurative language to convey their wisdom, there are also proverbs that are more straightforward and literal. For example, the proverb "A penny saved is a penny earned" is not particularly poetic or figurative, but it still expresses a valuable piece of advice.