Doesn't seem extreme at all to me. I used to work at a place that would stress the importance of keeping implementations easy to understand and documentation up to date in case "[team member] gets hit by a bus tomorrow and we have to replace him." (Some people apparently thought this was too macabre so they would try to change it to "they won the lottery and quit instantly," but the engineering team thought this to be a less likely scenario than getting hit by a bus)