There is no such thing as DNS propagation, only DNS cache invalidation, and by polling it, you are making your old records stay in more caches and for longer.
BGP, on the other hand, propagates.
BGP, on the other hand, propagates.
LRU does show up in resolvers, but as memory management: cache is full, evict the least recently used early. It can only make something disappear sooner than its TTL, never later.
It's time-based because there's no back-channel. An authoritative server has no idea who's holding a copy of its records, so it can't push an invalidation.