Yes, an exception to the rule is made for rulers of states. Just like in the US you have airports named after Gerald Ford, Ronald Reagan and GHW Bush Sr, in Holland living members of the royal family, I guess Mandela can qualify as well.
The idea behind this is, that ordinary citizens can more easily fall out of grace or do something controversial, like when they revert to killing or drugs smuggling. Chances are smaller Reagan will ever do that, but maybe that's why they wait in the US a few years for Clinton bridges, airports etc.
In Almere, a new developed town in the Netherlands, there was a bit of controversy because in the music area, there were streets named after current groups ("Rolling Stones straat") but also musicians like Jesseye Norman or Ella Fitzgerald who are or were alive when the city was developed. Like if they would feel for suddenly becoming a bankrobber or singing pro nazi lyrics !
nobody has ever died from hard work, but why take the risk?