I don't see why that's so special. Other data can have incrementing IDs or some other value. In fact all data can be considered to have a timestamp, at the very minimum being when it was inserted into the database, so it's a rather vague definition overall.
I think, its different because its dimension where usefulness of data goes does as the data ages. TimescaleDB for example, does optimisations ( they call it chunks or something) based on this fact.
Timescale is just an automatic partitioning extension for Postgres. You can also do it with the native partitioning feature, or pg_partman, or Citus, or other tools.
Partitioning the table is the optimization, so that you skip over data when querying and manage it in smaller parts, but Timescale doesn't do anything about older data and neither do most databases.