The Data Center ID has been in Snowflake IDs for a while. It's present in the original version of Snowflake that Twitter open sourced back in 2010 [0]. Looks like it was added in this commit [1] from August 2010.

[0] https://github.com/twitter-archive/snowflake/blob/snowflake-...

[1] https://github.com/twitter-archive/snowflake/commit/ba2e67ea...