This is a truth, but usually you leave a large enough amount that people can't argue you were swayed. I've heard of $2000 to $4000 being an amount for a larger estate.
This was used as a plot line in Better Call Saul. I wasn't sure it was something real but my understanding is that most of the cases used in the show are either real cases or composites.
To be honest, that TV show is heralded as being very accurate about lawyers