Fisherman," the concept is valid".
But does that mean that the Bible is actually truthful and we should believe it all and act on everything it teaches?
The fds parable would have been obvious to both the rich and to slaves that the slave's job is to work when the master is not present--and how pleased ("chuffed" is a good UK word) the slave would be to be found still working at the master's return. One of many everyday illustrations to sell the new bonkers idea of Christianity giving (mainly) the poor and uneducated the hope of immortality by worshipping Jesus.
Is it not obvious that the NT is the work of religious propagandists trying to convince and illustrate credibility for their partisan brand of the Christ story? You have to understand that the Christ story was known and told for centuries before Jesus appeared as the title figure. The Greeks called them Sophists, others; God-men, magicians or even conjurors.