That was an expression favored by leadership sage Stephen Covey to explain how distrust can only be repaired by behaving in trustworthy ways. Whenever we violate a trust or confidence, words can’t fix the problem. Apologies and regrets sooth bad feelings, but do not offer guarantees. Promises give others solace, but not permanent peace of mind.
I like the word "unwavering" here as it describes just about the best humans can get in accurately describing how humans engage with trust.
It's on a spectrum that can probably reach Zero but not ever all the way to 100.